It's nice to think about. But, as others have mentioned, it's not likely to work well in reality.

With that said, if Nintendo was able and willing to make it work, I'd very likely buy upgrades every couple of years. But, I'm a guy that hangs out in gaming forums. Is the average Switch owner interested in upgrading every couple years? Probably not.

I don't think this makes much sense, particularly with a portable console where, for a large part of the audience at least, they're going to be carried around and get a little beat up over time.

The closest you will ever see to this is maybe an upgraded dock, and even that will not do what you want it to. This will never happen in practice, otherwise we would all be on PCs instead of dedicated consoles. There is a reason the PS5 and XSX is about to release, and it isn't because the average Joe consumer wants to worry about compatibility with their games.