Maybe the EQG trailer is all a big bait-and-switch. Maybe there is only a very short span where they are human-form-ponies and the lion's share of the movie is the ponies we know and love.
Hmm, as I think about it I'm starting to look forward to the movie. I suspect that I'll either like it or it will be so bad that I'll laugh at it - whichever way it goes, I win.
Did you watch the new trailer? It's much better. It seems like the movie is taking the route I thought would be best for the movie: it's poking fun at how ridiculous the situation is and poking fun at itself.