I would not be so sure, the environment that led to the development of the SR71 is not there any more.

For one thing space based observation is very good and has a much faster turn around now days.

Back then photography was film based, satellites would fly take pictures and release the film in a pod to reenter and be recovered mid flight[1].

And on the other hand altitude and speed does not buy as much survivability as it did back then.

Fighters flew at a maximum of 1.5 mach and missiles at 2-2.5 mach.

S-400s for example can launch interceptor variants that can intercept targets at almost a hundred thousand feet moving at 14 mach. I know that is for ballistic targets, but I doubt an aircraft flying at a similar altitude even at hypersonic speeds would have much luck.