Boeing B-1R Lancer
The B-1R is a proposed replacement for the B-1B fleet. Boeing's director of global strike integration, Rich Parke, was first quoted about the "B-1R" bomber in Air Force Magazine. Parke said the B-1R (R stands for "regional") would be a Lancer with advanced radars, air-to-air missiles, and Pratt & Whitney F119 engines (originally developed for the F-22 Raptor). Its new top speed Mach 2.2 would be purchased at the price of a 20% reduction of the B-1B's combat range. This proposal would involve modifying existing aircraft. The FB-22 and YF-23-based design are alternative proposals.
The B-2 has proven itself in the "limited strike" role, able to penetrate any current air defense system and deliver conventional bombs with impunity. The role of "fleet in being" is ably served, and there appears to be no reason to maintain the B-52s for this purpose alone. This leaves the "bomb truck" duty as the B-52's primary role that is not currently filled by other aircraft.
Other changes in the nature of modern air warfare have also come into play. Missiles like the AIM-120 and AIM-9X so improve on older designs that the primary determinant of air combat success appears to be having the best radars and display systems the aircraft that can detect, lock-on and shoot first will almost certainly win an engagement, even, to a limited degree, against aircraft behind it. The idea of a "missile truck" for air-to-air combat has long been a dream of fighter designers, notably in the U.S. Navy (in the form of the canceled F6D Missileer), but these designs were always found to be seriously flawed when the missiles turned out to have disappointing real-world performance compared to their paper predictions. This era appears to be at an end, and the concept of a long-range heavy missile-firing air-to-air platform appears to be a practical possibility, even for a large and unmaneuverable aircraft.
Boeing's proposal appears to modify the B-1B into a design able to serve these two purposes. For the bomb-truck role Boeing proposes the modification of existing external hardpoints to allow them to carry multiple conventional warheads, dramatically improving overall warload. For the air-to-air role, both defensive and offensive, they propose to add active electronically-scanned array radar and allow some of the hardpoints to carry AA missiles. Even with its somewhat reduced range as compared to the original B-1B, its fuel capacity remains quite large. This would allow it to escape from unfavorable air-to-air encounters by simply running away; there are few enough aircraft capable of Mach 2.2 performance in general, and those that are deployed can maintain these speeds for very short periods of time.
In general terms the B-1R most closely resembles the original F-111 concept, as opposed to a pure bomber role. However it would be able to carry out these missions at ranges even greater than the F-111.