A genuinely green car is, of course, impossible. Moving a tonne of steel and plastic around could never use no energy at all and even the zero emissions hydrogen fuel cell cars will require prodigious amounts of energy to produce the hydrogen in the first place.
The switch to hydrogen is going to happen sooner than you think, though – the auto and petroleum businesses have seen the writing on the wall for hydrocarbons – but we mustn’t be naive enough to mistake the switch for a green initiative. The market is in motion, the economics of hydrogen will become very persuasive very quickly. Your next car may be one of these (from a useful survey of all the real-world green cars in The Guardian)