I hate to rain on anybody's parade, but. . . . The GM Hy-Wire is a neat idea, but it's old news, and GM themselves have backed away from it somewhat.
Hydrogen is really one of the worst alternative fuel options. The fuel is wildly expensive, it's much less efficient than a battery-electric car, and the only advantage it offers is fast refueling -- from one of the thousands of hydrogen stations that don't exist yet. GM were promoting hydrogen heavily for a while, with concepts like the Hy-Wire and the Sequel. They found that bringing durable, reliable, hydrogen fuel cells to market at a reasonable price was much tougher than they had imagined, and they were also very disappointed by the lack of action from governments and oil companies in setting up hydrogen filling stations.
GM still sees a potential role for hydrogen, more in China than in the USA. The Chinese have very ambitious plans to build 300 new nuclear reactors. The steam and electricity from those reactors could be used to produce large amounts of hydrogen more cheaply than most other sources.
They also found the "skateboard" design with interchangeable shells was much harder than they expected. The unsprung mass of the hub motors was a problem, and packaging was a problem. They still want to do the skateboard idea at some indefinite time in the future, after the technology matures more. But alternate fuels won't wait, they need something more conventional to put in the field before then.
In short, the Hy-Wire technology is on the back burner. Right now GM's R&D focus is on storage batteries and getting the Chevy Volt into production. They have described the Volt and its E-Flex Architecture as their "Manhattan Project".
There's also the question of whether GM will even be solvent five years from now. If you've been following the GM Death Watch over on The Truth About Cars, then you know what I mean.