If the rumors are true and we will be encountering the True Sith in KotOR III, then I hope that we keep the darker storyline initiated by OE. I'd like to get to the end of the game feeling a genuine sense of loss (if I'm LS) or of dominance (if I'm DS). OE hinted at this with the DS options on the Unknown World, and OE intended to do this with Malachor V. Hopefully we actually get there this time.
The request for a wider range of alien party members is a good one, but I don't know if it will be heard. Personally, I'd like to see a smaller number of possible party members, but more flexibility. Have 5 or 6 spots but give me 10 or 12 possible party members (some of which restricted to LS/DS, M/F). Keep the influence system, but have LS characters that storm off if I go DS and vice versa.
I will be very disappointed if HK and T3 don't return. 3P0 and R2 were the staple of the movies and I think the that devs have been wise to mirror this in the games.
I know that I won't make a lot of friends for saying this, but I hope that they do not change the game engine or the graphics. I know they are a little dated, but I don't want to feel like I'm playing a completely different game. TSL felt like a continuation of the first game and I'd like to see that carried forward.