I'm pretty sure there will be a KOTOR:3. The question is who is making it.
If it gets handed off to another company, I feel sorry for them. Despite the fact that they've got easy money to be made, following KOTOR:1 and 2 is not an easy task.
LucasArts was doing pre-production on KOTOR:3 a while back before their layoffs, so I think they definately want one. I'm sure there are tons of willing developers.
Why wouldn't there be one?