At the point Apple has squeezed all the revenue they can out of selling the two products separately.At what point do the MacBook Air and iPad Pro merge into a single product with a detachable keyboard?
There's no technical limitation to having MacOS run on an iPad when its attached to the Magic Keyboard (which also is way overdue for an upgrade). Unfortunately I don't think we'll see something like this for another 5 years (after every penny has been milked from the 2024 refreshed iPads).
Despite the growth in services Apple is still a hardware company and their priority is for customers to buy as many Apple products as possible, even if they overlap in all kinds of ways even though increasingly strained family budgets and attention spans would be better served with just an iPhone and a hybrid MacBook/iPad for most of our computing needs.