LLM usage is not very likely to "dry up".

What is more likely to happen though is that it doesn't take multiple $10B of datacenter and capital to build out models--and the performance against LLM benchmarks starts to max out to the point where throwing more capital at it doesn't make enough of a difference to matter.

Once the costs shrink below $1B then Apple could start building their own models with the $139B in cash and marketable securities that they have--while everyone else has burned through $100B trying to be first.

Of course the problem with this strategy right now is that Siri really, really sucks. They do need to come up with some product improvements now so that they don't get completely lapped.