KOTOR III is a must.
It should be next gen XBOX360, PS3, and Windows Vista. That force power pre vis video from E3 2006 is a good guide how how it should look.
A new Jedi character is a must. A greater range of charcater customization should be available, species such as Rodian, Twilek, and how about Jawa for a laugh?
Characters from the old games should return. I'd particularly like to see the Twilek chick from the first game (and I don't care about those who got the wookie to kill her). HK-47 is a must, I would like to see him meet Revan again and find out he was given "meat-bag" qualities.
The background of the game should be the rebuilding of the republic and the Jedi Order. Issue of how things should be done and the mystery of what happened to Revan and the Exile.
This would then lead to the Player character being sent to discover something by some of the old characters without being told what it is about in the outer rim. This then would lead to the player finding out about more of the past of Revan, the Exile and the Eternal Empire and the threat Kreia said Revan went to find.
Multiple ways of solving quests are a must not just light/dark. There should be interesting not straight forward options that yield more experience.
You should have a greater range of options for customization/upgrading. Also if you can't do it yourself you should be able get characters or merchants to do it for you. Upgrade sabres and weapons, your ship etc.
Also learning skills from trainers the same as KOTOR II such as Echani techniques, force powers, etc etc.
More mini games not just pazak, turret gunner, and speeder racing.
Also an interactive ship, ship databank that you can upload all the datapads to, add your own notes, star map.