Makoto will be a magical girl variant of the Undercover Model trope.In that she only got into the idol business to find Cure Loveads. Unless, of course, she was an idol before meeting Davi.
Ai-chan is Princess Marie-Ange in disguise.Given that the Princess has now been revealed to have pink hair and blue eyes, the probability of this has just doubled.
There will be four more villains named after the four remaining sins.
One of the Cures will be corrupted.And will be called Cure Joker.
Mana is a Tokusatsu fangirl.Though much more secretive about it than Yayoi/Cure Peace.
Joe is from the Trump Kingdom; either a knight or a member of the royal family.His name spells out 'Joker' when written in full katakana, he's definitely done something to help Mana transform into Cure Heart and was referring to her by her attack name even before she earned her powers. He must be from the Trump Kingdom, working to help Sword by getting her more allies and/or watching over her.
Cure Sword was actually part of a different Precure team before the start of the series.But something bad happen to them and that's why she was cold towards Cure Heart.
Joe will refer to all four Cures by their attack names.He called Mana "My Sweet Heart" twice in episode 1, so it's quite likely he will do the same for the other three, calling Rikka "Twinkle Diamond", Alice "Rosetta Wall", and Makoto "Holy Sword".
Mana will have a Broken Pedestal moment after finding out Makoto and Cure Sword are one and the same.
Rikka's gonna be the Butt MonkeyGetting screwed stopping people from taking advantage of Mana's kindness in the process.
Joe is actually a PrecureHe ends up being like the Sailor Starlights and is actually a female in a male's body who transforms into Cure Joker.
Davi is the managerIt's not like mascots turning into humans is anything new.
There will be a Monster of the Week created from the heart of one of the CuresAlmost certainly created while she's in her civilian form, and likely the result of a misunderstanding or argument between two or more of the Cures. So far the most likely candidate seems to be Rikka (due to having the least focus).
Joe is the Princess in disguise.Wouldn't it be effective for the Princess to disguise as a male, then surreptitiously hand out the Cure Lovies?
Joe is a fairy from the Trump Kingdom.Seeing as Davi can turn human, perhaps Joe is also a fairy who escaped from the Trump Kingdom's destruction. Except instead of helping the Precure transform, Joe's job was to give the Lovies to the people who he saw fit to protect the princess (in other words, he "knighted" them).
The princess has been brainwashed.The ...and Crazy is optional.
One of the Precures from Makoto's team is Not Quite Dead......and is in fact working for the enemy. In the OP, when the lightning flashes in front of (what is believed to be) the enemy King you can see a small dark silhouette that seems like a long-haired girl.
The Princess escaped to the human world.The strange light that appears after every battle and fixes all the damage is her doing. It's likely some skill exclusive to the Royal Family (called "Light of Restoration" or something like that.)
Speculation of suits for possible additional Cures...
Cure Rosetta will go berserk
Joe Okada is the Big Bad
Regina will be Doki Doki's equivalent to Joker.She may look goofy so far, but wait until she starts appearing more often.
Guesses for Cure Ace's identityMost people seem to think she'll be either Princess Marie-Ange, possibly having been reborn as Ai-chan, or Regina after going through a Heel-Face Turn. I'll Take a Third Option here and say it's a brand new girl, which would be a first for Pretty Cure.
The mysterious blue birdSo far, whenever the girls recover one of the Royal Crystals, a blue bird is shown to be observing them. There are a few possibilities for who or what this mysterious bird really is:
Regina is a Brainwashed and Crazy Princess Marie-Ange...Who will undergo a Heel-Face Turn and become Cure Ace.
Cure Ace's color schemeEpisode 14 introduced the Royal Crystals as five different colored items, each one appearing to correspond to an existing cure's color scheme except the fifth one, which is red. Therefore, it is very likely that Cure Ace's color scheme will be red.
There will be atleast two Sixth Ranger Precures.If Cure Ace wasn't a part of the Trump Kingdom's Precures, a brainwashed Precure will appear and make a Heel-Face Turn.
Regina and Ai-chan are both parts of Princess Marie-AngeMore specifically, Regina is actually Marie-Ange's Jikochuu (after all, Marmo did almost make one from her in episode 7), who was made to believe that she was always his daughter. (And if Regina is indeed Ace, this would sort of explain why she looks quite a bit like Ange when transformed.) Ai-chan, on the other hand, is the incarnation of all of the princess' positive energy, sort of like Chibi-Chibi in the Sailor Moon anime. Only when the two merge will Ange come back.
Regina is Marie-Ange's Long Lost RelativeHer sister, specifically. Yes, this does mean King Jikochuu is Marie-Ange's father. It's Royally Screwed Up, like in Suite Pretty Cure ♪
Related to the Cure Rosetta going berserk WMG above, she will eventually use one of her usually defensive attacks in an offensive way, a la Cure Mint.
Jonathan will transform into Cure Ace's mascot.
King Jikochuu has or had a human form.How could he impragnent a woman, unless he did it in the less traditional way.
The other fairies will get their human forms, too.
Last call for Cure Ace's identity! Place your bets!
Regina isn't actually King Jikochuu's daughterAs seen in episode 21, he doesn't seem to care for her at all. Obviously, that's because he's King Jikochuu, but still. Not to mention, Regina looks very...normal for being the supposed daughter of an Eldritch Abomination. My guess is that she's some random girl who the villains took as a baby for...unknown reasons. Maybe she comes from the Trump Kingdom?
Regina will become a Precure in the thirtiesEither that or she'll die. Her theme color would be probably black, white, orange or red. Yes, Cure Ace has already red, but her costume is mainly in white, so if Regina become a red Cure, her costume would have more red parts than Cure Ace's. Black is one of her main colors. White is the opposite, symbolizing her Heel-Face Turn. Orange is the closest color to red, though brown is also a possibility, but who would choose brown?
Some of the Selfish Villains will undergo a Heel-Face TurnBased on spoilers for episodes 25 and 26 it is possible that Mamo and Ira will both pull a Heel-Face Turn.
Regina has a weak heartWhy else would she have let herself fall for King Jikochuu's latest (and potentially most deleterious) trick in episode 22? This is part of the reason why Setsuna didn't return to Labyrinth until Moebius was defeated and Labyrinth at large is revealed to not be as evil as previously thought–she had enough strength to withstand Northa's hypnosis until Pretty Cure showed up to rescue her.
Alice owns an islandJust like Karen. If she hasn't, maybe something similar like a mountain, land etc.
Similar to above, Alice owns the Clover Town StreetIt's said that the original name of the town was Yotsuba Shopping District, similarly egocentric named as the TV channel in Doki Doki.
Marie Ange, Regina and Aguri are all sistersIt would explain why both Marie Ange and Regina had a resemblance to Cure Ace, Regina's connection to the Royal Crystals, why Regina's heart hurt when she saw Ace, the reason Ace needs to fight, why Aguri speaks so formally and why their names have a certain similarity to them.
Marie-Ange is a Xanatos-Gambit
The legendary Pretty Cures◊ are Heart, Diamond and Rosetta's predecessors.With Marie-Ange being the leader and Heart's predecessor.
Cure Empress was Cure Heart's ancestor.Pink eyes and a pink costume.
Bel will take over Regina's "The Dragon" role.He already tried to kill her and he killed Leva and Gula. This guy is the most evil character after the Big Bad.
Regina joins the Cures and gets one of the remaining two MacGuffinsPossibly the Eternal Golden Crown. Regina has blue eyes, she has glown in a blue light and the crown belonged to the blue Cure. Regina's name means "queen" and there was an evil organization called Eternal. The Miracle Dragon Glaive would also fit, as one of Regina's theme colors is red. The red Cure has also a ribbon on her head. The glaive is owned by Marie-Ange, but we haven't seen it again.
Cure Ace has lost to the two remaining Selfish Agents (Pride and Lust)Neither the Selfish Trio nor the Selfish Deputies nor King Jikochuu himself didn't know her. So it is possible that she lost to unknown enemies.
The members of the Selfish Trio can fuseLeva and Gula did this before. So it's possible that at least two of the three will fuse.
If Mana gets a male Love Interest in series proper...Without taking whoever gets her in Non-Serial Movie into account, place your bets here!
The movie is either canon, or at least has some of its elements be referenced later. Or both.Self-explanationary. As for the timing, it's probably set in between episode 38 and 39.
Prediction for the other two Legendary CuresMuch like how Cure Empress had green hair and wore mostly pink, Miracle Dragon Glaive's Cure will have red/pink hair and wear blue, and Eternal Golden Crown's Cure will have blue hair and wear green.
At some point during the final episodes, Regina will pull a Heroic Sacrifice for Mana's sake, and disappear into light in Mana's arms.Considering how family unfriendly this season happens to be compared to previous seasons, this seems to be a plausible theory.
Regina and Aguri are connected in some way to the princessThere have been many hints foreshadowing a secret about Aguri.