Until the energy density of batteries allows people to drive 100's of miles and refill quickly, internal combustion is not going anywhere.
With the production of that much energy in such a small space, the combustion engine would pretty much be obsolete and the entire world would have access to power at virtually no cost. Build the reactor... and that's it. Getting hydrogen is just a wee bit simpler and cheaper than getting uranium, oil, or coal out of the ground. Not to mention the impact it could have on space craft, space stations, satellites... you name it.