Please, if this is true, tell me Twilight consumed the rest of the mane 6 to increase her magic power and is now the villain. She may or may not have enslaved Chrysalis as her chief minion while she was at it.
Mane 6 (and everyone their age) “turns” into elders. The elders are “gone”, and the foals are now the adults. Then G4.5 continues of the same universe, but with everyone aged. It’s now focusing on CMC, and other pre-school foals as the main characters.
…oh, and Twilight is now a bigger princess, and works closer to Celestia and Luna. Twilight doesn’t turn into an elder, just like the other princesses haven’t.