By 2552, Hood was essentially the leader of the United Nations Space Command, as well as the only known active member of the UNSC Security Committee. Whitcomb and Ackerson are dead, and most of us will have never heard of Nicolas Strauss. Having taken control from the UNSC civilian government sometime during the Human-Covenant war, Hood is essentially a military dictator. A necessary evil, considering what humanity was facing at the time.
But now we hit a snag: The war is over, the Covenant destroyed, and humanity still in existance. Being the only member of the Security Committee left, would Hood give up his powers as humanity's leader?
If he chooses not to, he has little to stop him. He commands the UNSC Defense Force, and however tattered it is after the war, it would be able to stop a civilian protest. Furthermore, he has the resources of the Office of Naval Intelligence at his disposal, which can pump out pro-Hood propaganda, proclaiming him the saviour of the human race, etc, ect, and if there is resistance from vocal figures who could sway the masses to them, we have seen before that ONI does not have a problem with assassinations.
So, there you have it. Hood could easily set himself up as the dictator of the human race should he so desire to. If there are any Security Committee members left, they could simply rule as a cabal where there word is law.
Of course, it is always possible that Hood would simply give up his emergency powers and return power to the legitimate civilian government, but that doesn't make as good reading.