Unfortunately I haven't had the chance to play TBC beta, yet i read lots of stuff about the new instances and stuff and I didn't see anything about Uldum! Anyone knows if anything is going to be implemented down there someday? maybe in the first TBC patch?

No mention of it that I can recall. I imagine it fell in the bin marked "Grim Batol etc". The first TBC "content" patch will be Black Temple, if I remember correctly.

Mystery Solved.