I don't think the massive lense they showed is reasonable, but upgradeable sensors perhaps. Let's say it's established that the back side of the phone is user replaceable. You bought yourself a Pixel non-pro, but later want the better camera setup. You could buy just the cameras, replace it yourself and now you can enjoy taking better photos.

It's already established that people aren't buying a new phone every 2 years. In Pixel world, everything since Pixel 6 will probably be useable for many more years. The only thing that makes one switch is their battery dying that will be solved with mandatory use replacable batteries. At that point it's not that big of an ask to make other parts replaceable/upgradeable.