There are plenty of news, papers, magazine covers, that ask the same question: "Will hydrogen replace oil?"
The question is ill-posed, and that's why.
Hydrogen is NOT a source of energy, it's just a way to store energy for later use.
Therefore you cannot compare hydrogen and oil, you should instead compare hydrogen and batteries, for example.
Unfortunately, there is no hydrogen available in nature on the Earth, and therefore we have to produce it. To produce hydrogen you need energy: exactly the same energy that you later obtain from consuming the hydrogen that you produce.
Therefore it is true that a hydrogen-powered car does not pollute the environment while running.
But the plant that produce the hydrogen for that car is instead using energy and possibly polluting the environment.
Unless, of course, you produce hydrogen from wind and solar, which is nice, but impossible at the moment.
The amount of power used by private transportation (cars) is much greater than the amount of energy that you can produce from a reasonable installation of solar panels. Unless you cover all the countryside with panels, you will not obtain the necessary power from the sun.
Hydrogen is still interesting as a research for the future, hoping that solar and wind will improve their potentiality.
And it is also interesting right now, if for example you produce hydrogen from coil / gas / nuclear, and you power your cars with hydrogen, because you avoid the pollution inside the cities, which is a major cause of deadly illnesses, for example.
So, when you read about hydrogen cars, keep this in mind. They are not solving the problem of where to find energy, they're talking about how to store it.