From what I understand the SR-71 has been retired. What has replaced it another airplane or maybe data you get from satellites made it obsolete?
It's been replaced by dragonladys and satellites in the main. however, the ISR role has also been taken up by UAV's such as Global Hawks, Predators,. various smaller UAV's even submarines have some of the roles. The US for example also has access to other assets which provide a system view on a point of interest. eg Compass, Rivet, Guardians, ASW aircraft also perform more ISR roles as tech has improved.
sateliites didn't replace them, satellites were prefered because they were benign, and the fact that no pilots would be put at risk.
The US stopped ferrets over the soviet union as russian SAMs improved, but they didn't stop overflights over the soviet union until the late 70's.
they stopped overflights over china in the early 80's. IIRC their last overflight over a foreign "hostile" country was 82
satellites can only do so much, unless you have sympathetic conditions, unless the satellites are tailgating (for overlap and redundancy) then they are limited.
aircraft (manned and unmanned) provide control and immediacy, satellites don't and can't. you just can't reprogram them to change course and harvest over a new area at short notice.
in short, the SR-71 was replaced by a system, - not by a platform