Personally I'd like to see Manaan.
I loved the whole Ahto City part of KotOR and - given the fact, that we are at the brink of an all out war where kolto would be direly needed - it would make sense, too. Ahto City could be the other neutral place where both factions can trade with each other. Or secretly try to gain control over the kolto for that matter.
Ah, well I'll just wait and see I guess.