the funny thing with there being a cgi yoda for a future release of phantom menace is, that Peter Jackson is doing something similar with using the Gollum from Two Towers and Putting him in fellowship of the ring for a future release. Andy Serkis obviously should be used, that prototype gollum in the first one always bothered me anyway.

as for lucas, he won't stop just with the prequels, oh no. He'll completely replace chracters with digital ones in the original trilogy probalbly starting with artoo and yoda. But why stop there, he'll probalbly do a cgi lightsaber duel for the death star in IV, add the emperor in a new hope and show alderaan from the surface as it is blown away. Being unhappy with the actors original performances he'll do digital edits and redo them, adding lines to sync them up with the prequels.