Yeah, what oddspyke said. Most cars today can mechanically roll on for nearly forever, in car lifespan terms. The question is, do you want to be driving it at that point? Even since I purchased my 2016 R, the improvements/additions in safety electronics, the digital dash, stuff like that just in this model alone have been fairly significant, and if you look at other models, particularly more upscale models, each model year seems to bring some new thing that often is actually rather desirable. And that's not even counting the issues of stuff like firmware updates, software updates, system interactions, etc.
As cars become progressively more like aircraft--a bundle of integrated mechanical, electronic, and processor-based systems--how we view the age of a car is going to shift. I suspect that eventually we'll be seeing the car as a platform, like say an F-16, where you can do product improvement programs over the years to plug in new parts. Well, that would be the engineering solution; from a commodity/marketing POV, that probably won't happen because manufacturers want to sell you new stuff all the time.