I don't think that TUF has run its course at all. TUF4 might have been a step back, but like KillerG said, it's a great way to attract new fans - I know I'm here because I stumbled on to TUF3, for instance.
I think the TUF concept will run for a while yet.
1. a finishing stroke; anything that effectually ends or settles
2. discharge or release from life.
3. a period of retirement or inactivity.