The consensus within the hydrogen community is the lack of an infrastructure to provide the hydrogen needed for the fuel cells, the most efficient power source for theses vehicles. The problem is soluble, but it will be solved by a power company rather than an automotive or hydrogen producer.
All proposals involve massive infusions of government funds.
None are seen as being possible before 2010. It appears that the use of hydrogen as a common vehicle fuel is a quantum leap. It is, however, possible in small steps.