Saw one of the promos just now....
Twilight using a spell that makes them fillies again..... (I know of alot of fan art of this from the past 2 years).
Bronco Bro is probably right on his theory of what will happen in the wonder-bolt academy episode. (THey show RD racing with a mystery character.
Late to the party on watching it but I was trying not to but the Hub decided to give make me see it during the rerun of Too Many Pinkies.