I’m betting 2021, with an App Store only ARM-based macOS, and dual/contemporaneous boot with iOS, starting with a consumer iBook that’s close to the price of an existing lower-end MacBook.
Dual-OS bang for the buck for the consumer, higher margins (no ‘Intel tax’).
But I wouldn’t necessarily recommend getting that 1st-gen machine, or any of Apple’s 1st-gen hardware for that matter.