Apple might well do a lot of research and early engineering on a car, but that doesn't mean it won't drop the idea before it hits the market. It's done that with other new ventures before. I suspect this one will drop too.
Why? Because the car business is difficult, complex, sprawling and littered with legislation, lobbies and entrenched rivals. And its profit margins are tiny. BMW has done its i cars because it sees new mobility as the only way it can survive. Tesla launched itself because its founders have an evangelical mission: to end the grip of petroleum. Google posits its self-driving car as another project for the common good: to reduce the vast casualty toll especially in countries where mass motorisation is new.
But Apple isn't an evangelist company any more. It looks that way, but what it really loves is profit. Why would it bother?