Now thats an interesting possibility.
Personally i don't think VA jobs will die, there'll just be less of them, especially minor ones.
Possibly, VA's will sell their normal acting services as well as databanks with their samples alongside the rights to use them (or whoever will own the rights to their voices). There'll probably be stuff like using "illegal samples", aka using samples without authorization, which would be something similar to how we treat piracy.
Of course, none of this could apply only to voice acting necessarely.