I have an "old" electric car. (2018 Leaf) I've noticed some of the issues you allude to.

There is a Nissan app that doesn't work for the car anymore, because the car has a 3G cellular radio in it, and there just aren't many, if any, remaining 2g/3g towers. It does have android auto, which so far I don't care for, but that's probably a skill issue. The car has navigation, but the maps are out of date and Nissan isn't offering updates anymore. It has Sirius XM, and I think I could just turn on the subscription and it would work. Lastly, the "rapid charge" port on the car is a CHAdeMo port, and there are fewer of those than NACS or CCS.

Outside of those things, the car works like any other EV. All menus and screens operate and all the accessories work.

Whether or not something will last as a "classic car" depends on the same thing as it always has: the number of weirdos interested in that car. There aren't huge groups of people trying to keep Chevy Chevettes or AMC Concords alive, but there are huge online communities and even some cottage industries that have risen up around things like Jeeps, Suzuki Samurais, air-cooled Volkswagens, old BMW's, and yes, Nissan Leafs.

Sure. The shell and possibly drivetrain will be original, and the electronics will be replaced. Just like all those kits to make electric vw buses (though they will still run just gine on gasoline. l