Ooh good one. Tbh, I think they'll focus on new races rather than classes as they've covered all the major ones and there's not much left. That said, how about:
Imperial Commander: Sort of the opposite to the Trooper, but with greater emphasis on tanking and buffs. Basically like the Powertech to begin with, minus the gadgets and with the option to branch into pure tanking (Dreadnought, based off the Destroyer Droid in aspect) or support with buffs and healing (Sternguard, based on a sort of Commander Cody). Trademark skills could include using an ARC Blaster or activating a back-up Droid.