I do not believe that another bomber ever needs to be built.
Maybe not, but in GW1, Afghanistan 2001 , Kosovo, and GW11, resistance on the ground was broken by B-52 cluster bombing, not precision weapons.
Those B-52s will not last forever, and a platform capable of delivering high tonnages of devastating hell on ground enemy formations will always be a needed and key arrow in the quiver.
Whether the B-52 replacement will be manned or not is a good argument. I have no problem with totally automated, robotic warfare, so long as we remain at the leading edge of technology. Sadly, I think our advantage there has been neglected in favor of income equality.