Well, to be honest, I don't think there's a immediate need to replace the HMMWV (stand for High Mobility Multipurpose Wheeled Vehicule, is not HUMVEE) because of a few reason.
1- in his basical role of troop carrier, ambulance and light recon and communication vehicule, it's perfect, but you cannot ask this thing to do everything, basically, it was design to patrol in low-danger zone (mean were there only a risk of been shot at with light firearm, not some air bomb or RPG). SOF have they own version of the HMMWV called the GMV (Ground Mobility Vehicule, a kind of long-range HMMWV like the British SAS patrol version of the Land Rover use in 1991)
2-The 3rd picture is a picture of the US National Guard...
3-When IED can destroy M1A1, do you think that a "nimble" HMMWV" can survive ??
4-In Afghanistan (this is a low-danger zone!! not Iraq) The Canadian Armed Force were using Iltis Jeep at the beginning, we refused to use the HMMWV that the US borrowed to us, after than a Iltis rolled on a mine and 2 infantryman died, the investigation conclued if we have use the HMMWV for patrolling, those soldiers will be still alive. Recently, we start to field our new G-Wagen that have similiar protection than a armored HMMWV, a IED exploded when a patrol of G-Wagen was rolling, all the crew survived. If we have use HMMWV, the resultat will be the same, all crew will have survived.
5-News don't talk about those who life was saved by the armor, only those who died...