The season four finale is approaching! USA Today posted this short clip from one of the upcoming episodes, titled "Twilight's Kingdom". Like many finales before it, it is a two-parter. The finale will air in an hour long special on May 10, 2014 from 10 - 11 A.M. EST. Here are the episode descriptions:
When a villain escapes Tartarus, Princess Celestia chooses Discord to help track him down instead of Princess Twilight. Meanwhile, prompted to prove that she has an important role to play, Twilight turns her focus to opening the Tree of Harmony chest.
In order to protect their magic, as well as the fate of Equestria, Princess Celestia, Princess Luna and Princess Cadance transfer all of their magical power to Twilight.
Clip uploaded to YouTube by Lyra Hooves.