The problem with the car analogy
The problem with the car analogy and identity is that it confuses brand and similarity under one identity while ignoring "brand name as concept"--the way you can "Xerox" something on a non-Xerox copier. (Technically, you can't. But people used to say it, and everyone knew what they meant.)
You want to compare 3E/3.5 to 4E, Pathfinder, and any number of products. You decide that 3E is a Chevy car, 3.5 is a later model of the same car, 4E is a Chevy truck, and Pathfinder is a Toyota car. Which is more like a Chevy car, a Chevy truck or a Toyota car? Well, assuming you picked fairly standard models, and the conversation already assumes a bunch about the exact activities that you are going to be using--you have all but guaranteed that people will say that the Chevy Car is more like the Toyota than the Chevy Truck.
But no reasonable person is going to say that the Toyota car is really a Chevy and the Chevy Truck is not. Partly, because no one cares to try to stake out anything on the identity front in that analogy. And partly because neither Toyota nor Chevy are recent (Xerox-like) terms for "car".
If GM bought out a Toyota plant (ha!) and started producing the same exact cars under the Chevy label, those cars that used to be Toyotas are now Chevys. And that's what people would say about this mysterious model X for awhile: "Oh, that's the Chevy that used to be a Toyota." But note that already, it is a Chevy. Eventually, people would forget, and it would just be another Chevy. The same exact thing would happen if WotC bought Pathfinder: "Oh, that's the game that used to be a D&D clone but is now one of the D&D versions." And eventually, it's just another version of D&D.
The reason for that is the same reason that no one can pin down exactly what D&D is--beyond a "state of mind" and what the producers of games call those games.

There is no single "D&D" that everyone can point to (not even OD&D) as the definitive thing.
You can play a D&Dish game with Fantasy Hero. I did it for years, playing in the Forgotten Realms even. But never would any of us have said we were "playing D&D". We were playing Fantasy Hero in a (mostly) D&D-ish manner. When we play 4E, we are playing D&D--in a 4Eish manner. When we play AE, we are playing AE--which is always a bit D&Dish by design. When we play 3E, we are playing D&D--in a 3Eish manner. When we play an AE/3E mixture, we are probably playing D&D in an AE-ish manner, but it could be the other way around.
To say that something is or isn't D&D beyond the scope of brand identity and "state of mind" is to acribe more definition to "D&D" than is possible.