From a commercial standpoint GMC has already stopped making the H2's and H3's. However, it seems the H1's are now going to be phased out as well. Apparently the US Military aren't happy with the Hummer, to small and to lightly armored. They are going to be replacing their line of Hummer's with another vehicle.
As this youtube guy said, to big and gas hoggy for the public, to small and weak for the military.
Seems like this is the final death nail for Hummer's.