Spoon!
Almost a dozen years, when the Mac App Store was introduced, there was a lot of teeth-gnashing that Apple was aiming towards a MAS-only version of macOS that would lock out outside purchases. Apple shot that down that concern, but I wouldn't actually be too surprised if an Apple-regulated version of macOS was being reconsidered.
As long as 'regular' macOS for Mac machines continued (and there's no reason why not), Apple could offer App Store-only A-series dual-OS iPads as a more easily-managed, updated, and security/privacy-oriented alternative in the vein of iOS. You wouldn't have to buy it if you didn't want it, but maybe a lot of people would go for it. I don't know.
As someone who loves his iMac and iPad mini, I'd personally consider going for a (large) iPad Pro if I could run Mac apps and have iPad apps too.
But I think that the Surface machines show how grafting touch onto Windows is sometimes good but usually a kludge, so I'd hope that if this was true then touch/Pencil support would be intelligently but very lightly integrated into macOS itself.