I think it was pretty obvious based on episode numbers at this point, but Meghan McCarthy has confirmed that the season finale will in fact be a single parter, similar to season one. She also let everyone know that M.A. Larson (Magic Duel, Cider Squeezy, Ect) is the writer for it.
And finally, in other news, Corey Powell will be the writer for Just for Sidekicks. She was the same one behind Sleepless in Ponyville, so I'm pretty sure the rest of the season is going to be epic.
Thanks to Dan and Kein for the heads up!
(and in other, other news, I think Zap2it derped one of these episodes, unless we are going to see a new cast of ponies for one of these!)