Here's a crazy idea though... what if they essentially recreate the Clone Wars but in the OT, by having something like REBEL WARS set in between Episodes 4 and 5? They could fit in a few seasons worth of battles or stories.
Not crazy at all. I'd rank that right up there as a likely guess along with continuing Ahsoka's story, post-Clone Wars, and doing a post-ROTJ series (if needed to keep from stepping on Luke, Leia and Han's movie toes, they could focus on a new set of characters and have the biggies come in for cameo appearances.)
I know zip about KOTOR, but on the assumption that that era is important for merchandise, that's a contender too. Can't forget about selling those toys!