It'll happen in games first.. nobody cares if 'background NPC #15' is generated by AI, and mostly they voice a few sentences at a time.
Suddenly, voices aren't special.. Voice actors have to have something else, like movie or book fame (Audible books seem to be mostly voiced by the authors, and I can't see that going away). But only a few % really have that.. I bet there are thousands of voice actors we wouldn't even recognise the names of.
Wars are already simulated like crazy. AI battles will be going on right now working out if various ukraine battles are winnable, what will happen if Iran gets too riled up, etc.
The bit we currently do wrong is then verifying the results using real people..