The only other major thing for repairability/upgradability would be less glue on the battery and threaded inserts, which doesn’t add size.
The glue was reduced on later versions and especially on the OLED version which also got threaded inserts. So those are already done and I doubt the next version would regress in that regard.
And given some recent news about Valve working on an ARM emulator and funding Arch Linux to help them start supporting ARM as well they might be working towards that. Though if that is for the deck 2 or something else further in the future is yet to be seen.