I'm sure it already does happen to some degree. But the only limiting factor would be the cost/benefit analysis of doing that versus just hiring a more bankable actor.

I can imagine some time in the future when an actor's digital model keeps pulling in money while the genuine article's own career starts to go downhill.

Also an interesting (for certain values of interesting) development would be hiring caucasian actors and digitally switching their race around rather than hiring POC. Esentially the million-dollar version of blackface. Some studio's bound to try that in some subtle way and it's bound to fail horribly.