The B-52 lives in an awkward niche. Bomb trucks over utterly unprotected airspace might just not be a thing anymore.
If that holds for the forseen future, the B-52 will not have a real successor.
Currently, it looks like non-precision bulk bombing is just obsolete.
We "depend" on the B-52 because it still works, and there's a lot of chance it shouldn't get a replacement.
Are there any other planes we "depend" on that are old but not being replaced? Our tanker fleet is old but we are looking to replace it. Maybe some transports are getting old? But they probably don't need a new design. EWACS is old but also seeing new systems being built.
The C-130 is ubiquitous. https://en.wikipedia.org/wiki/Lockheed_C-130_Hercules
The US plans to replace both JSTAR and AWACS with Golden Dome? https://en.wikipedia.org/wiki/Golden_Dome_(missile_defense_s...
The B-52 has hands with the JASSM, ALCM, LRASM. No need to get close to pack a punch. Yeah a successor would likely be a LO blended wing body design, but the idea of cheap to operate big truck is fine.