** The end of Hackintosh as we know it **
Today's momentous announcement of the transition to Apple Silicon means that Macintosh will
eventually become a completely closed and proprietary system.
But this won't happen right away. There is plenty of time.
Probably, you're correct.
So, for me, it just means that there's no real incentive to buying Intel based Macs anymore and paying such a high premium to do so. Sure, I would consider buying an Intel based Mac at a very significant discount, but not at the current pricing.
I know of some Mac Pro users who've kept their original Mac Pros (pre-2011) for ten or twelve years, but can you really do that when they've been EOL'd now? For instance, the migration from PowerPC to Intel showed that the sale of PowerPC machines dropped radically after that transition was announced.
I was considering buying a Mac Pro, but no, not now, not at the current pricing. They've essentially been discontinued (the long slow way, of course). No reason I can see to pay a premium for that kind of system.
There are a lot of compromises in buying a Mac (particularly in graphics cards), and I'm glad I've kept my Windows up to date. I'll keep my hacks running (until they don't) and will switch to Windows when I have to, but I won't be buying anymore "real" Intel based Macs any time soon at the prices Apple currently charges. I'm seriously considering selling my Macbook Pro 16,1.
Soon, can't tell you exactly when, many buyers, particularly corporate and agency buyers, soon they will realize that buying a Intel based Mac will be a bad investment and they won't pull the trigger on a purchase.
I've working in Silicon Valley for many years, and I've actually spec'ed out equipment, and never, ever would any CEO or CIO approve purchase orders for equipment that's been discontinued - not even with such a really long transition time.
EDIT: I left out the conclusion of my original post. The upshot of what I'm saying is that if the sale of Intel based Macs drop significantly, Apple will have no choice other than to speed up the transition, which means things could happen much faster than what your chart proposes might happen.