While we yet don’t have mechanisms to update to Nextcloud in place we can already share that upgrading will be a painless progress requiring minimal user interaction.
For the server this is probably easy for manual upgrades. Changing the repo or install a new updater app as well.
But how do you want to replace all the clients?
Reinstallation There will be new clients and apps out as soon as Nextcloud is released … Desktop & Mobile Apps - #54 by przybylski