There are actors and estates of deceased actors who already have licensing arrangements for the use of their likenesses. If I recall correctly, this came about several years ago when Ginger Rogers bitterly sued some company that had made a commercial using some footage of she and Fred Astaire that had been digitally altered and recontextualized. Not quite the same thing as virtual actors, but that's what woke Hollywood up to the issue. This sort of thing became directly relevant to the Poser world when DAZ released their Anna Marie Goddard virtual clone package, as I'm sure many here recall. :-)
In hope and trust that there will always be a place for live actors. They play's the thing, and there are nuances of human expression which aren't as exciting when duplicated. I think that WETA's Gollum is the most amazing virtual actor yet by a long shot (sorry, JarJar,) but let's not forget that MoCap technology and the very fine actor Andy Serkis are what gave Gollum the better part of his expressiveness. Director Peter Jackson insisted that the CG animators follow Serkis' cues at every stage, and not "correct" his acting. In fact, at one point, they were instructed to re-design Gollum to look slightly more like Serkis himself. Can't wait to see ROTK!