In theory they could offer the Mini with eighteen different CPU options, but that's not really their style.
https://www.anandtech.com/bench/product/2520?vs=2584
The 3990X costs more than ten times as much as the 3700X. It has eight times more cores. On anything threaded it smashes the 3700X. On anything not threaded it... doesn't. In many cases it loses slightly because the turbo clock is lower.
It basically means that the processor with the best single thread performance is somewhere in the lower half of your lineup and everything above it is just more chiplets with more cores. That's perfectly reasonable for servers and high end workstations that scale with threads. I'm not sure how interesting it is for laptops. Notice that AMD's laptop processors don't use chiplets.
On the whole my guess would be that we have the iPad Pro and MacBook Air using the same SoC, the MacBook Pro doing… something (it'll still need integrated graphics, but do they really sell enough to justify a new die? OTOH they do make a die specifically for the iPad Pro, and I'd guess it's lowest-selling iOS device v. highest-selling macOS device, and idk how numbers compare!), and the iMac (Pro)/Mac Pro using chiplets.
The silicon team is going to be very busy: they've got the A-series, S-series, T-series, H-series, W-series, and U-series chips to pump out on a regular roadmap.
The A-series (CPU / GPU / Neural accelerator) is the major work. It gets an annual revision, which probably means at least two teams in parallel?
The A-series X and Z variants seem to be kicked out roughly every second A-series generation, and power the iPads. The S-series seems to get a roughly annual revision, but it's a much smaller change than the main A-series.
I could see the Mac chips on a 2-year cycle, perhaps alternating with the iPad, or perhaps even trailing the iPads by 6 months?
Of course, yield is still a physical constraint, but apple sells a wide range of products and shouldn't have any trouble finding homes for defect-ridden chips.
Whom is Apple going to sell binned A14s to?
Where does everyone think margin comes from in the chip business?