The Hub has released a teaser clip for this weekend's episode (March 10, 2012).
Season 2, Episode 20
It's About Time
"When Twilight Sparkle receives a strange and vague warning about impending doom and disaster from her future self, she drives herself nearly mad in an attempt to stall a cataclysmic event, but her uncertainty makes finding answers difficult."Via EQD & MutatingRaven