Many analysts are expecting that fuel cells will be the future replacement for our current Lithium-based battery as a power source of mobile devices. It may be true, but it will still require years of development, as shown by a recent demonstration carried out by Toshiba:

It shows a prototype able to power a notebook for 10 hours.
While its shape makes it somewhat usuable, its size is currently not compatible with maintaining the mobility function of a notebook. Toshiba expects to reduce the size of components in order to transform this fuel-cell module into a flat case that would be located below the notebook.
Additionally, the fuel cell generates too much noise, at this time.
JCJ