There probably won't be a next "Stealth Bomber". The days of the manned, penetrating, large, long-range bomber are drawing to a close. The B1 and B2
were the last of their kind - the last strategic bombers intended to penetrate enemy airspace themselves. Instead, we will see more UAV's and stand-off weapons launched from platforms unable to "break down the door". If there is a new large bomber, it would probably be a "Bomb Truck" used mostly like the B52 is used today. It would fly in from long ranges to launch cruise missiles and drones before the enemy air defense is defeated, and would drop guided bombs from high altitudes after air supremacy is attained. BWB's are especially well adapted to that role, because one big difficulty in designing a BWB is making the fuselage strong enough to be pressurized. Bombers don't need the whole fuselage pressurized - just a smaller compartment for the crew. The same basic design could be used as a tanker, or even the same aircraft could perform both missions. We would have bomber/tankers rather than tanker/transports.
It is the need to penetrate enemy airspace that makes bombers expensive and hard to maintain. Since we have standoff weapons, UAV's, fighter-bombers, etc., we don't really need that capability anymore. When all you want to do is drop bombs on forces that can't attack at high altitude, or launch long-range cruise missiles, the old B52 does just fine. All a new large, long range bomber would have to do is replicate the capabilities of todays B52 - but with more efficient engines, a 2 person crew, etc. Since the main fuselage does not need to be pressurized, it could last a long time, perhaps even 50 years - as long as the B52.
SHORT.....The next large bomber will not be a replacement for the B1 and B2
but will be a different kind of aircraft entirely, with a completely different mission profile. It would do the same jobs the B52 does today, while non-bomber types take over the penetration mission. The BWB could be a good choice for that kind of mission.