I think you're looking at this with the 'innovators dilemma' problem of expecting cars not to be designed with the idea of upgradability in mind. Maybe Tesla ha

I think you're looking at this with the 'innovators dilemma' problem of expecting cars not to be designed with the idea of upgradability in mind. Maybe Tesla has been thinking this way all along. Upgrading an interior probably has too much diverse meaning to meaning (does it mean dashboard? seats, console? etc), so let's leave that one for now, but I think the rest of the issues you mention have possibly already been addressed. Older parts don't have to be more expensive, because we'll be able to 3-d print metals, or assuming we're talking about an electric car, there are less mechanical parts anyway and a company could decide on a modular design that they stick to for efficiency purposes. For instance, Toyota could decide on a shape and size of their batter pack. Then as battery technology inproves, they don't have to create a bunch of stock to upgrade old cars, as the old cars would use the same design as the new. I agree with you regarding smaller spaces and closer quarters, but technology is also constantly shrinking too, so I think it might be possible that replacement/upgrade parts could be smaller than the one they are replacing, so as long as they share a mounting structure, it won't cause a problem. You are right about entertainment systems, previously there was a standard (I think it was called DIN) size and there was only one size. Then they added 1.5x and I think 2x sizing. But upgrading your entertainment system used to mean getting an aftermarket system, not a system from the same manufacturer. Now, it seems to me, that manufacturers use the same or a very similar system across their brands. They aren't stocking 100s of different systems, they are stocking 5 or 6 and those are used across all of their designs. If upgradability is thought important from the design stage, I think all of this is possible, and more.