Apple's shareholders would riot if the company started building its own semiconductor fabs.
The cost of a current top end fab is astronomical for experienced semiconductor companies. There is no "skunkworks" to get a top end fab going.
The real prayer is that Moore's FIRST law / node shrinks run fundamentally out of steam in producing efficiency or speed results, and that gives the entire industry time to optimize and drop fab equipment costs for near-top-end fab performance. This may actually start to happen in the next 5-10 years.