Absolutely sales of laptops would continue.
The areas where the iPad beats the MacBook are still (imo) the same as the day it launched: web browsing, watching video, and reading. Workloads that are heavy on the Apple Pencil too, but that’s a fairly narrow slice compared to anything else you might do on a computer.
I don’t see anything in my use case that I’d gain from a MacBook over this setup.
Let’s just ignore the price comparison though lol
A MacBook is optimized for a larger screen and comes with a better keyboard and trackpad.
I use both my MacBook and iPad all the time, because their hardware form factors are better for different things.
I don't want to read books on my MacBook and I don't want to do development or writing on my iPad.
I briefly tried using my iPad as a Mac through the screen sharing. It's not as useful as you are imagining.