Ok in the SDCC q&a about mlp they said in season 6
You may see a return of a villain or two, but not in the way we think.
The only villain I could think of that may returned are ether Queen Chrysalis, or maybe King Sombra.
What do you guys think?

I like that evil ram. I bet he was like "I AM THE MOST POWERFUL BEING OF EQUESTRIA!

AND YOU MERE POWERS OF YOU WORMS CAN BE ABLE TO COMPARE TO MY GREATNESS." Yep.

I bet Grogar should be a big power-hunger who seek for conquest of Equestria.

4559588
Sombra? Nah, he was blown to smithereens. Chrysalis would be a good possibility. While they may not be villains, Flim and Flam would be another possibility, I don't see those two clowns learning from their mistakes.

If she's not an antagonist anymore, I'd like to see Trixie return.