Well, with EPUB-based E-Readers you download the file and upload it to the device (via USB or WLAN or something). So even if the built-in shop is closed and you cannot directly load from the internet, you can still download and read new books. On Kindle though you can only use the online service. Therefore if the device is unsupported it will be impossible to get new books, even if the device is perfectly fine and perfectly able to display even newer books (because how does book technology change really - it is words on a screen). Depending on the way it is handled, it may still be able to read the books downloaded to the device at the time the service stops. Although Amazon certainly can delete books on customers devices.

In short capitalism strikes again.

No idea.  My kindle can download books anywhere, maybe something changed with the communication chips?  Or amazon is just being a Richard?  Who knows.  

This.  I just started Skies of Arcadia.  Still want to play Link Between Worlds and Twilight, with the latter having 4k textures and at a higher framerate.

I also want to give the remastered bloodborne a go.