Possibly that's true with the body casting and dual-glass, but there will be a massive difference between the Intel Atom and the Ryzen that will only exponentially increase in the years to come. Tesla's in-car apps are just going to get bigger and better, but the Atom is already essentially at its limit with this current-gen of apps. It simply won't be able to keep up in the years to come. And unfortunately the evidence of the Atom's effect is sitting in the UI itself right in front of the driver, and it will be one of the very first things a potential purchaser sees as they monkey with the MCU.
It's the same concept as cell phones. Cell phones have in essence a planned obsolescence, not because the hardware is designed to fail (although that is up for debate), but because the apps of tomorrow are built to take full advantage of increased processors capabilities that older cell phones simply don't have. If you tried running today's apps on an Iphone 4, that thing would barely work because its hardware is a small percentage of the current gen's capabilities. And I see no reason it would be any different for Teslas in the next 3-5 years.
I really want a Ryzen. Will I reject a car without it? Probably not. But will it markedly impact my re-sell if I hold onto it for more than 2 years? Almost certainly.