Well, the Studio and the Pro already have
removable/repairable storage, so there's clearly no technical barrier. As far as anybody can tell, the only reason it's not
upgradeable - even with genuine Apple parts - is down to Apple's policy of only selling you like-for-like replacements. (There are conflicting reports of whether upgrades work, but that could be because you have to install exactly the right combination of modules). That said, simply having the possibility of
replacing a perishable component like SSD if it fails is a plus for the Studio/Pro.
The other interesting development on the RAM side is that, until recently, LPDDR RAM has only been available as surface-mount chips - so
all thin laptops and small-form-factor systems that use LPDDR have been non-upgradeable out of necessity (Apple did have an excuse there). There is now an emerging standard (LPCAMM) for
plug-in LPDDR5X modules - so it will be interesting to see what that does for Apple's competition in the future.
As for Apple adopting LPCAMM, the words "over", "freezes" and "hell" spring to mind, not least because they seem committed to mounting the RAM chips directly on the SoC package - however, I do have a lovely mental image of a future Mx chip with plug-in "wings"...