It will be a while until season 4 comes out. So in the meantime, why don't we come up with some ideas for episodes they might add. I have two ideas.
Discord to the Rescue:
Discord tries to prove to everyone that he has reformed by doing good deeds around Ponyville. But no matter what he does, everyone still thinks that he's evil. He then discovers that Sweetie Belle has been kidnapped by the Diamond Dogs and they want Rarity to give them 2,000 gems in exchange for her. Seeing that Rarity doesn't have that many gems, and how worried she is about Sweetie Belle, Discord goes after the Diamond Dogs and tries to rescue Sweetie Belle.
The Lone Zebra:
Cheerilee has her students interview someone in Ponyville for a school assignment. Apple Bloom decides to interview Zecora, since she knows nothing about her backstory. Zecora tells her about how she came from a small village of zebras and she was separated from her family during a bad windstorm when she was just a filly. She goes on about how she tried to find her family and her search lead her to the Everfree forest, where she believes that's where they are. Apple Bloom feels terrible for Zecora and decides to help her find her family.