Switchblade Concept

"As far as the last time the USAF was concerned with a high speed bomber, I would point you towards the B-1, the Valkerie, Hypersoar..."

Yeah, all history except the B-1 which is subsonic in its current incarnation.

Some future bomber may be faster, but in practice it hasn't been relevant for the last few decades. They have simply been 'bomb trucks' for the last few wars, and that is very much set to continue as far as I can see.