On to the history part:
Nabu's new host is Khalid Ben-Hassin, who is a Doctor of Archaeology and Hawkgirl's partner in excavations/expeditions to ancient sites in Egypt. Khalid is himself a native Egyptian, but was raised by none other than Kent Nelson (who we know met his death under mysterious circumstances).
To say that Khalid is Nabu's new host is a bit incorrect, as it appears that Nabu no longer takes full possession of who ever wears the Helm. Instead, Nabu is more of an adviser/teacher showing Khalid how to work his new powers. The new Dr. Fate has recently defeated Nabu's old nemesis, Wotan, and has teamed up with Green Lantern and the Flash to stop an upcoming menace to their planet.
It is noteworthy to mention that Dr. Fate no longer sports his classic blue and gold uniform. Although, his look is very close to the classic Dr. Fate, his colors are now black and gold. Also, the black portions of his uniform appear to be more of a galaxy contained within his body.