Admittedly, Nick and Tai, a Derpy episode could be doable... it'd just have to be handled delicately... and Hasbro's pretty much dedicated to just keeping her in the background after The Last Roundup backlash...
That being said? I've heard rumor that villains (as in, not Trixie) will be making a return. Maybe more NMM? More Discord? Chrysalis being a recurring pain in the plot? who's to say?
... I'm voting for all three, for the record. It'd be nice to have some hamminess from the Darkness, the Chaos, and the Cute Monster Girl of the baddies.