Virtual studios have been doing this for a decade or so - there are always four or five vendors at NAB doing this sort of thing. Granted - they aren't making the talking head look like C3P0, but that's evolutionary, not revolutionary. One of the Canon C300 demo shorts used live compositing of background and foreground elements for green screen back in 2010. Worked pretty well. Can't remember what it was called, but if you're not interested in rendering the characters, the rest of the stuff isn't that tough to do real-time. Working on'n'off on a project about Veit Harlan where we're doing everything but the characters and costumes as 3d renderings in real time. That's been the plan for 5 years now. So yeah - this is sneaking in more and more than you'd think. Lucasfilm's evolution is, as Lucasfilm is wont to do, simply a matter of replacing the only human things left with pixels.