Wild Mass Guessing for My Little Pony generations other than the fourth. Guesses for My Little Pony: Friendship Is Magic go here.
Humans are the source of all evil!Or, more specifically, humans are the source of the "villainous" entities in the Ponyverse. The Talesverse lacks both humans and the frequent assaults of said villainous entities. As both continuities are set in an explicitly magical universe, it could be argued that humans somehow subconsciously generate the evils when in an area with magic. In fact, one could conceivably do some Arc Welding and say that at some point between the two series, humans were barred from ponyland specifically because of this trait....
Generation 3 ended when the ponies fell under a reverse-aging spell they couldn't cure.The first sign was Rainbow Dash's voice getting higher. Then every pony got smaller. Then they were babies. Sure, the ponies may claim they were "remembering" what they did at that age, but why is the same gang of seven all together in the baby series when that group of friends didn't form until the later G3 videos? They're really just describing the deja vu they experience as they try to deny the fact that they're about to shrink away to nothing.
G3.5 is AU or non-canon from G3There are far too many continuity errors.
G3 ponies are magnetic, that's why they can use Invisible AnatomyThe toys have magnetic hooves so why not? For the things they hold that aren't magnetic.. Then maybe it's magic, or everything is magnetic in the Ponyverse?
G5 will be even better than G4Because they'll know what they did right in G4.
G5 will recieve tons of hate from butthurt bronies regardless of its qualityPretty self-explanatory. In fact, I'm sure this definitely will happen to some extent.
Glory and Moondancer are marriedThey did have a porcelain called "Wedding Prance" where they appeared to be getting married.
G3 is set after G4It makes perfect sense: the two alicorn sisters went with the wild whipper. All the ponies with similar names are decendance of the mane six
Reeka and Draggle's father is the MoochicThe Moochic and Hydia are on the same vague power level, and are about the same size. And it's not as thought there are many humanoids around Dream Valley.
There will never be G5.After the success of Friendship is Magic, anything else that Hasbro puts out might not be as good. And if videos like this are any indication, the fans will eventually be able to produce their own full episodes. With these, Hasbro will hire these animators and voice actors to continue the trend and thus continue G4 for a very long time.
After G4 we'll hit another Dork AgeThis seems to happen every few years. Hasbro will make the cartoons an All-CGI Cartoon and other changes will cause distress within the fandom. The ponies designs will be hated by all.
Ponies are segregated in G3 due to Fantastic RacismIn one of the G3.5 specials one of the ponies quite literally says that Sweetie doesn't belong in Ponyville, she belongs in Unicornia. Pegasus and Earth Ponies haven't interacted in so long that the latter forgot the former existed. Earth Ponies are afraid of Unicorns powers, Unicorns traditionally think they're better than other types.
If Hasbro creates a new My Little Pony movie, it will be Human Focused Adaptation due to Executive MeddlingThe human involved would either be Megan from the G1 cartoons or an Expy thereof.
G1 ponies have ridiculously short life spans (by human standards)That's why we rarely see background ponies more than once.