Never?
Jobs didn’t agree with App Store. Or pencils.
Keyboards and mice were seen as accessibility options not mainstream…
Never say never
Steve Jobs' objection to "pencils" was to their role as a NECESSITY for input and device interaction.
This is a common misconception.
Keyboards and mice on the iPad are STILL optional, and ALWAYS will be.
While I agree that no one can predict the future, we can take an "educated" guess regarding macOS on iPad
(iPad haters WILL NOT like this):
1. Apple is a business... they WANT you to buy both a Mac and an iPad (for as long as they can get away with it)
2. Apple (and 3rd-party developers) has been already developing and releasing iPad versions of heavyweight Mac apps
3. Every new version of macOS looks and feels more like iPadOS, NOT the other way around
4. Apple has been giving the iPad Mac-like capabilities like Stage Manager, mice/trackpad support as ways to address iPad / Mac parity gaps
5. In the end, iPadOS & iOS are BOTH based on OSX aka macOS (Steve said iOS IS OSX in the iPhone intro keynote)
6. Apple is using "mobile chips" on their desktops. And "desktop class" chips on iPad. Mac/iPad hardware consolidation is 99% there already (base and mini iPads are the holdouts).
And this is the BIG one for me:
7. An OS designed for touch can be easily navigated with a cursor, but an OS designed for a cursor cannot be easily navigated with a finger. You end up with the Windows experience (which FWIW many can tolerate, but not me)
Given the above, I predict that Apple will keep bringing the iPad capability closer to the Mac to the point where it'll be moot to have macOS around at all. We will have appleOS and iOS (Apple forked iPadOS away from iOS for a REASON).
Think about it, the paradigms are there already.