If you thought three years/releases were long, you better brace yourself because how soon do you think the X design will be fundamentally changed? My guess is never. There is nothing to change anymore when the front is basically all screen. They will release different sizes and colours and eventually get rid of the notch (but not as soon as you may think/hope), but that‘s about it for the smartphone concept as we know it wrt exterior design. Maybe foldable screens will become a thing, but that will also take quite a while and maybe something completely else like smart glasses will be here faster and replace the smartphone itself. In the meantime, the X is what you get.
Yeah, I suppose you are right. They can always do different things with the chassis I guess, but major design innovations are likely going to be a thing of the past. Ive been waiting for this moment for years. Different size screens, and different display technologies for future builds. Heck. Displays themselves may be obsolete in the future.