The comments on the Wired article are pretty brutal, and I would echo some of them, such as this being just a pitch to the Air Force. It's probably not as advanced as the Mach 5 Skylon/Sabre/Scimitar concepts the British are rendering. The real breakthrough will come when someone renders a plane cruising at Mach 8.
Skylon has an advanced propulsion system (or will have) but the SR-72 has a totally different purpose, and needs to be able to deliver weapons on target.
Certainly there are already planes that have gone faster than the SR-72 might, but none in the same job.
I understand the reasons why the want this plane, but I still feel we have the assets to do the job now(minus the attack profile it would have). We are going to have to look at reduciung the over-inflated defense budget at some point...most likely before this plane would ever enter service.