These 20 series cards are deliberately overpriced so they can sell off the huge overstocked 10 series cards
Have you got any evidence of Nvidia dropping support/gimping in the way you describe? I'm heard that before but I think it's a myth that's been debunked?
You'd be much better off buying a 1080ti off eBay. Got one for 460 quid brand new.
Just need SLI 2080Tis and pray the game supports SLI decently if at all.
There are definitely 4K 144 Hz screens on the way if they're not already available. I think Asus have one due anytime now.