[tomsem]

My working assumption ('prior' in Bayesian terms) is that WiFi devices are not going to get cut off any time soon.

It's based on nothing in particular apart from the fact that so far the only Kindles that have ever been cut off will be the cellular only models on Feb 24, most of which lost wireless connectivity some time ago. Even then they will still 'work' and you can side load anything in your digital library after converting it to mobi.

My Kindle Touch still has Kindle Store access. Why would they cut it off? If that's the case with the K3 and KNT as well, then I don't see this happening soon.

Cutting off Kindle apps has precedence: Amazon doesn't control the OS platforms and isn't going to support versions which the OS vendors themselves have sunsetted.

At some point Windows for PC 4.2.0 will stop working, but I think it will only be done as result of some refactoring or major change to the app that they want to push out (like to make it look like the Android and iOS apps, and let you view Scribe Notebooks).

I think had WSA (Windows Subsystem for Android) not been deprecated by Microsoft, they would have continued to rely on that as the preferred Windows solution. It was clunky having to install Amazon Appstore as well but didn't cost them any significant development resources to implement.

Perhaps what will eventually replace the native app will be Kindle for Android, with an emulation layer so it runs as a native app without WSA or Amazon Appstore to install it. It would only need to emulate the subset of Android OS APIs which Kindle app uses. They'd then only have 3 code bases: Kindle embedded, Apple iOS (macOS via Catalyst), and Android. Amazon surely has the resources to pull that off.

As for hardening on-device DRM they certainly had ample opportunity to do it with the 2024 Kindles, and they did not take that opportunity. So it's not clear they have intention to do that any time soon either.

It's prudent to keep in mind that they have ability to do so at any time.