And iPad with macOS would be unusable as a tablet with regular mac apps (macOS requires more precision control and has smaller targets), and at best would be a way to get a Mac to hook to a monitor and use with a mouse and keyboard. But you can already get a Mini for half the price, or an Air that also comes with a keyboard. So what exactly do you gain? Especially if they also come up with a M1 Macbook (no Air/Pro, the small version).
What Apple could do however, is further improve iPad OS multitasking and windowing use to make it better for multi-app workflows.
Already basic multitasking, window-tiling, drag and drop, and file Finder support, and USB-C have improved it dramatically for such purposes.
That said, Final Cut Pro, Logic, XCode and a Terminal would be nice additions...