The X-43A was a rather crude demonstrator, relying on a large, heavy copper heat sink and burning hydrogen, but the X-51a is much more advance, and much more viable technologymuch lighter, and being actively cooled by its own hydrocarbon fuel, and the flight ready SJX61-2 scramjet has finished ground test

It will start on ethylene, and than sustain thrust with JP-7, the fuel used by the SR-71, and should have a powered endurance in the 300 second range, following launch at 50,000 feet by a B-52 and a boost to supersonic speed by a booster derived from the ATACMS missile.

I think that if this transitions to anything in the near term, it would be some sort of missile, and if they can get 300s thrust at mach 5 or so, you would be looking at a total range on the order of 600+km.

One of the things that would change is that you would see a lot less metal, and a lot more composite.

Picture Pr0n below:

SJX61-2 Engine in Hypersonic Wind Tunnel

Titanium nozzle for SJX61-2

The fuel tank is integral to the structure.