Not sure why one needs 8K60p on a phone. Files are absolutely massive even in ProRes LQ. 4K120p is welcome though for up to 5x slo-mo. Also if you can offer 8K60P you can offer 4K240p.
It looks like the iPhone 16 Pro and Pro Max will both be capable of up to 8K 60 fps video, thanks to the new camera sensor and A18 SoC, although Apple may limit the iPhone 16 family to 4K 120 fps, instead. The iPhone 16 Pro and Pro Max will both also reportedly come with a minimum of 256 GB of storage.