Apart from a lot more animation work needing to be done its also an issue with regards to bypassing a lot of stuff, likes traps, encounters etc etc. Makes developing content a lot harder I would suspect.
Oh, I don't expect flight to EVER be a thing. The framework of the maps and such just don't fit. Though that said, you still run into the problem of "I can get exactly one character past this obstacle and that's it." And for a game that depends so much on party cohesion that's not too helpful.
Which is why I said that Aarakocra and Protector Aasimar are going to need some minor stat reworks. The animation isn't too big a deal because they've already done it...reference the Cambions in the tutorial.