Rolls-Royce has started testing on the replacement engine for the B-52, which was selected in 2021. The new engine, the F130, is set to replace the current P&W TF33's outfitted on the Stratofortress fleet. The TF33 engines have been in service for 6 decades, racking up over 72 million flight hours during that time. The new F130 is based on the commercial BR725 engine which can be found on the Gulfstream V & Bombardier Global Express. Rolls-Royce is planning to develop the F130 to remain "on-wing" for the next 30 years of service life for the B-52, meaning the engine will remain on the aircraft for all maintenance (hindering an engine failure.) It's estimated Rolls-Royce will produce 608 of these new engines (8 engines per aircraft, 76 in service) with an additional 42 in reserve, but no official numbers have been announced yet.
Photo source: https://en.wikipedia.org/wiki/Boeing_B-52_Stratofortress