You can currently do uninterupted Upgrades already.
Here’s how.
Once you have version 1 completed copy your app and spreadsheet to version 2.
work on version 2 up to completion.
When you are ready to deploy version 2. switch the glide names around. Give version 2 app, the name of version one app,
There you have your first upgrade without interrruption.
The data from the old spreadsheet can simply be copied or appended to the new spreadsheet for continuity without anyone losing data.
You can also have a “Standby” version of your app that lets your users know that their app is currently in upgrade mode, and will resume shortly.
So if your app name is “Michael’s App”
Make a copy called “Michael’s app v2”
Work on Michael’s app v2
change Michael’s App name to “Michael’s App” V1
Change Michael’s App V2 to Michael’s App
The key really is in the name you give to your app, not in the app itself.