There will be a KOTOR 3, just as there will be a Halo 4(there is an in-game cutscene that proves this, Just finish Halo 3 on Legendary and wait till after the credits), a Assasins Creed 2 and a Super Mario Universe. Do you know why?
MONEY, the reason the Star Wars Prequels ever happened, why EA make the same game over and over again and the same reason theres going to be a COD 5(which just lost 40% of its because its going back to WWII). Supply and demand is a big thing, the fact that everyone is talking about it now means that Bioware/obsidan will make it, but they will try and drag it out, as this will increase hype and sales. but Lucasarts wont let Bioware announce it yet because of The Force Unleashed, as it would divert attention from it to the sparkly KOTOR 3. I would expect an announcement in E3, if not Christmas 2008