Yeah, that is the danger I tried to allude to in my second paragraph.

I hope we do see phone/OS/store ecosystems that focus on longterm stability of features and UI. Keep devices repairable by end users, supply parts for the whole of the phone's lifespan.

Fair phone is trying to do this for phone hardware, and Framework is doing similar for laptops. We still need OS and store ecosystems.

Yup, "smart" devices will require an accompanying phone of a similar age with the app already installed in case it was removed from the App/Play store -- if you want to keep using it much after 5 years.