In the future...
CGI will advance to the point where movie stories will be complete scripts: action, motion, blocking, dialog, facial expressions, intonation--all will be captured and digitized, parameterized, and stored.
In the same way that the character Woody in Toy Story is generated from scripts, all characters will be scripted. But with ReverseCGI (tm), those scripts can be back-calculated from any performance. And, in fact, all the great Hollywood movies will be parsed. These will be fed into vast libraries of actions, characters, and scenes. To build a movie, then one just needs to annotate the script with necessary blocking and expression. Then, you select your actors, scenes, and voila! A new movie is generated. Or with RoundTripCGI (tm), an old movie is edited with new dialog, plot, replaced actors, etc.
At first, only high-end shops will be able to do this, but eventually, it will be simple enough to do by casual users, like mix tapes.
Since the algorythm will know how to parse Elizabeth Taylor's facial expressions as she delivers line X, her tone, inflection, and expression can be cast on any line of dialog. It will be possible to pair her young self with a young Brad Pitt in a remake of Sleepless in Seattle. Egad!