Okay going to be a buzz kill here. The B52 of now is not the B52 of the past. It was designed as carpet bomber. However in the world of precision munitions, carpet bombing is just not needed. But no matter what decade you are in, war still requires a shit ton of munitions and some way of hauling them. The B52 is that munitions hauler. The reason why no replacement, is simple, good luck trying to convince the Pentagon to spend a shit ton of money to design, engineer, and build what is essential a giant glorified truck. As weird as it may seem, it makes economically sense to keep the old girl working.
Being pedantic. Wayland is a replacement not a successor. It’s for those X does it, why not Wayland, situations.