What Tesla is saying is even weaker than that. They're not saying they'll ever provide such software. They're really just selling you a car with the claim, "its hardware is sufficient for self-driving; now all you need to add is the software." Or to put it another way, "if we ever release self-driving software, it'll work on your car" (or otherwise presumably they'd shoulder the cost for being wrong about this guarantee).

That's still more than they could say for fusion drives, but it doesn't imply they will ever provide you with any self-driving software. Just that they believe it's possible to write such software.