I base my guess on the fact that the SR-71 has been retired, but that mission
profile still exists. There has to be something that has replaced it that
isn't
public knowledge yet.

During Balkan campaign some of US military-technological capabilities were not
even known to top military leadership and they were not allowed to use them
during the conflict as they were not supposed to know them.(need to know rule))
This policy was the reason of some resentments in military circles after balkan
conflict.