There are three major aspects currently separating the Mac and the iPad: cooling, sandboxing, and windowing UI. Let's consider each of these in turn.
Cooling: Even with the M1, it's not going to be solved for the iPad without making it noisy and heavier to the point that degrades its usability as a tablet. In general, no matter how efficient you make your CPU, you can always get more performance by running more of them faster and at least high-end Macs will continue to want that. Not necessarily Macbooks though.
Sandboxing: Application sandboxing is becoming more of a thing everywhere in computing. Ubuntu's Snaps are one prominent example, and Homebrew is a limited example on the Mac. And MacOS has been increasingly sandboxing the system as well. That leaves the user's files. In iOS Files has been making strides in opening up here, so it's not impossible to imagine that they could meet in the middle.
Windowing: Here again there have been convergent steps in both directions, with iPadOS multitasking and Mac full-screen modes. But the gap is still quite a large one, depending on the user. Many users even today use their PCs and Macs almost always in full-screen mode for one app or another. On the other hand you have users who like to use windows and spatial organization and feel harshly confined on the iPad. Being in the latter group, I hope Apple finds a way to expand windowing capabilities in iOS. If nothing else it would make the experience of using an external display on an iPad through a dock much more reasonable.
However, since none of these are insurmountable and trends beyond just Apple are all moving in the same direction, Apple will likely continue to converge the platforms as they've been doing, and then one day will, for example, phase out Macbooks once iOS has come far enough. (And yes, I think it likely iOS will "win" - - it's newer, cleaner, more efficient, more widely used and developed for, and still shares the same core unix kernel as MacOS.)
EDIT: I left out touch vs mouse interface on purpose. Apple's already made a lot of progress converging here, both making touch apps work with a mouse for Catalyst, and promoting trackpads and gestures on the Mac. There will always be apps where one or the other interface works better, but that will be the whole point of the converged device: use a mouse OR touch wherever it's more suitable.