Which do you think will be the next step after fossil fuels?

I think electric is the way to go, I feel as though if hydrogen cars take over, someones going to have to much control of how much your paying for hydrogen in your car (like gasoline/diesel) compared to electricity which is basically everywhere. They're both roughly the same price now, the avg MPG for hydrogen is about 50 - 60 MPG and electric if converted to MPG is about 100 -  120 MPG. Electric has to be the way to go, there's so many easy ways to make it.

The future of cars doesn't start until Yamauchi says it does. (cuz gaming discussion lol)

well it's 2015 so this year we will get hoverboards making cars obselete...

Conspiracy:
There was a huge rumor about mercury based power sources during WW2. Nazis were investing heavily in that to levitate things. IMO that tech might be a surprise introduction when fossil fuel ends.

More real assumption:
Hydrogen fuel might take over.

Mostly single-person self-driving electrocars in cities and probably self-driving ethanol cars for sporadic out of city trips. The cars as they currently are is plain inefficient and dangerous concept.

When we find a way to charge more quickly and have it go over 200 miles on a single charge is when electric takes over. It's a good idea but is too inconvenient for the average customer right now.

There won't be "customers" in 20 years. Transportation companies will operate swarm of small electrocar taxis around the city which you will call from mobile device. I've read a paper on subject, prognosed costs of a trip in such a taxi is so less than conventional car you gotta be a complete lunatic to own one. Not to mention you'll be taxed into hell since human-drived cars are a huge hazard and any sane government will just abolish them when they can.

Four words: Water-Soluble liquid compound. :P

I doubt they'll have enough employees for thay endeavor, and it might take off in large cities like NYC but the technologies won't be perfected enough for either having enough taxi drivers or self driving cars. 

Plus most conservatives and many liberals would hate not being able to have the freedom to drive. 

good question, both have pros and cons, but i thing H² will win in the end. its much easyer to integrate into the grid.
wind and solar work good with H² or synth CH4, but not that good with E-cars. and the loading of a H² car is much faster than a E-car.

but in the end it all comes to the german inustrie, they are the one to choose how we drive in the future, why? because they have the highst r&d expenditures, the best chance of bringing in new tech (its much easyer in costly big cars) and germany is leading with the transition to clean energie. we allready have some small power-to-gas facilitys.we also have a lot of biogas that needs costly upgrading or mixing with clean H²/synt CH4 and enough surplus energie at times because clean energie is volatile.