WMG / Disgaea 4: A Promise Unforgotten

Disgaea 4 will go Meta-recursive, and will make its serious moments an over the top parody of its own Sliding Scale of Seriousness Versus Silliness
The second Promo suggests it. And the games into video has hints of it too.
  • Confirmed. One scene has the characters being depressed over succumbing to the recently spreading "A Virus". The A Virus transforms the victim into Axel. Also, most of the character deaths are played with as the dead character either turns out to be alright or got better too quickly or the reaction to said death is needlessly over-the-top.

The obligatory second mode will star Fuuka
There's already at least one piece of art with her in the human world - in her "pre-Prinny" life. The second game mode, like the Axel mode, will be a prequel to the main story and cover Fuuka's descent into delinquency, but uniquely, will take place in an alternate modern day human world, filled with monsters and the like.
  • NI come out and said that they are indeed planning a DLC mode for a popular Disgaea 4 character and Fuka is one of the more popular characters of Disgaea 4 so...
    • Confirmed. The secondary mode will be about Fuuka and Desco.
  • I have come up with a possible plot for the scenario which will star both Fuka and Desco if the recent Disgaea 4 popularity poll is any indication:
    • They have already taken over the world and now Desco is acting out her role as the final boss. Unfortunately, every hero who comes to their doorstep falls easily and doesn't give Desco that thrilling climatic final battle feel. She gets more and more depressed as one by one, the heroes fall to her. In the final chapter, Fuka betrays Desco, which really pushes her off the deep end and the two engage in one final heated battle. Desco finally falls, but Fuka tells her that she betrayed her only because she didn't want to see her depressed anymore and wanted to give Desco the final battle she had been craving for a long. Desco is so overjoyed to see her Onee-sama care so much about her, but Fuka tries to brush it off Tsundere-style.
      • Alternatively, a Non Standard Game Over could be added to the final battle in which Fuka loses and Fuka, with her dying breath (At least if she's still capable of actually dying at this point), tells Desco the true reason for her betrayal and this is when everything goes to hell, possibly to make up for the lack of a Downer Ending in the main game.

Desco and Asagi will team up.
Asagi wants to star in her own game; Desco wants to become a final boss. Clearly a match made in the Netherworld, and they simply must join forces — all with the intent of eventually facing off in their very own spotlight title, of course...!

The Netherworld the game takes place in? Axel's home world!
Disgaea 2: Dark Hero Days has the last chapter taken place in a children's orphanage where building contractors have been commissioned to build an Overlord's castle. Axel stops them, of course, but that doesn't mean the castle doesn't ever get built. Cue Time Skip, and Overlord's castle is finished, with the antagonist as the Overlord. That explains how the Dark Hero is without a cameraman or director in sight; he's home!

Valvatorez will be voiced by Yuri Lowenthal.
He looks the part...

The names of angels are actually Nom de Guerre.
It would explain why there are now two people named Vulcanus: the events of the first game led to the first becoming Unpersoned, and his Code Name and ranking were assigned to someone else. As for why Flonne got to keep her name after becoming a Fallen Angel, she never exactly disobeyed Lamington's orders...plus, the audience is too used to calling her Flonne by now.

Fuka's father wanted and needed Fuka to die.
Given his reaction to seeing his dead daughter, either he truly is insane, or having her die was part of the plan all along. A human, even with two final boss sisters, would have trouble taking over the world in his mind. So, by having her die, she would have to end up in Hell since her ambitions are not Heaven worthy, as he says. By killing her, he sends her on her way to become a demon, makes Deso fall to Hades as well to find her, and BAM now she can take over the world. He... just didn't think or know about the whole Prinny roadblock thing.

By the time of Disgaea 4 Father Salade has died and gone to Celestia
He's now working as the uniform designer for Angel Trainees...
  • It might have been earlier than Disgaea 4. La Pucelle has always had an uncertain chronology...

Valvatorez got the title of Tyrant from defeating Baal
Unless the Japanese is different, Baal is the only other demon to be called a Tyrant, and that's how it worked in the original Disgaea.
I believe there was a bonus boss in Prinny 2 who is also a Tyrant, and is seemingly unrelated to Baal.
  • I remember that that prinny is actually Baal's reincarnation.

God and Baal are somehow related, though how is uncertain, whether it being the same entity in a different body or what not.
One of the more common forms for Baal's multiple bodies is that of an Enryngi. What does "God" manifest as? An Enryngi. With God Is Evil being in play in the 4th game, it may be possible.

Someone at NIS is a Castlevania fan.
The plot to late the game has some disturbing similarities to the back story of Symphony of the Night. Artina plays the role of Lisa, Valvatorez plays the role of Alucard, and Nemo plays the role of Dracula. To elaborate, the circumstances of Artina's death are in many ways similar to Lisa's (both die as a result of medicine related No Good Deed Goes Un Punished). Valvatorez is pissed but is stopped by the dying words of Artina. Nemo goes nuclear as a result, becoming a dark lord of sorts hell bent on the destruction and punishment of man kind as retribution for Artina's death.

The Chara world is inside that characters mind.
The Chara world is essentially a character equivalent of an item world. You go inside Him/Her/it, beat up enemies, and solve geo puzzles. Now this would be all fine and dandy if it wasn't for the fact that you can DEPLOY THE CHARACTER YOU ARE CURRENTLY INSIDE, INSIDE THEMSELVES! Inception jokes inside, this instantly rules out you being physically inside them as this would create a paradox. Therefore you are most likely actually inside their minds and are beating up nightmares and when you deploy them you are deploying their imaginary self who if dies results in that real character going into a coma which is why they cannot be used again until they are healed at the hospital. The geo blocks are probably their latent abilities.

God is YHVH.
Think about it, God is a jerk to the residents of the Netherworld and Earth.
  • Possibly Jossed by the Vita version's extended ending, where Valvatorez suspects that the entity that brought out Fear the Great is not God at all.

Gig and Prier knock each other out
Both of them were too strong for the game's cast, so they just stood back and them Mutal Kill each other, except they're not dead.

Lamington was orchestrating the events of the 4th game.
We get clues to this in the DLC Tournament arc with Mid Boss as the final fight. We know those two are allies and the real objective of the tournament. Lamington's piece in the plan was Artina, with the objective being getting Valvatorez into posistion. Arch Angel Flonne is in the know (or at least more so). Much like the 1st game, the plan required using the personalities of all involved in some way (Artina, Flonne, Valvatorez) to get the desired results. The net objective was to protect a certain human world from Fear The Great and whip said world into shape, which might also involve a Zeroth Law Rebellion.

The Fate Revolution Circuit is trying to drain God's power.
When too much celestial energy settles into one being; it becomes like Baal or Pringer X; an Eldritch Abomination dedicated to a corruption of purpose that isn't compatible with the world.
  • The Creator set up the Fate Revolution Circuit to to counter this by appointed a human being with a fraction of this power (thus draining it); and throwing them at whatever Demon Overlord is causing the most problems at the time. (Some Black Wings are created for just this purpose.)
  • Most human God pro tems die; which goes along with the plan. Should one be successful; the process is designed to kill the host anyways; and prevent them from continued access. Then the "White Wings" move to another base in an Alternate Universe with another Demon Overlord to throw temporary Gods at; in an Unending "Final Battle between Angels and Demons."

Valvatorez got his title because...
He crossed the street without washing his hands. Every. Single. Day. Knowing this series, it's either that or actually being evil.