It has been announced that Elijah Wood, Andy Serkis, Christopher Lee, and most importantly Sir Ian McKellen as Gandalf will all bt returning to Middle Earth for the upcoming Hobbit films. I am unsure how I feel about all these cameos in the films, but as long as it is done well, I think it could work. Hugo Weaving has not been confirmed as Elrond yet though. In other news David Tenant of Dr. Who fame is being rumored to be Thranduil the Elven King. That could be pretty neat.
For the Full Hobbit cast, visit the one ring.net by clicking here.