The U.S. Department of Defense has told the U.S. Air Force that there will be no more money for developing a new heavy bomber. Not for a while, anyway. That will slowdown the decade long air force effort to get a new heavy bomber, but won't stop it.
Since the late 90s, the air force has been U.S. Air Force is working on a replacement for its current force of heavy bombers (19 B-2s, 67 B-1s and 76 B-52s). Models of what the new bomber might look like have been shown, and the "B-3" (officially the NGB, or New Generation Bomber) looks like the B-2. There were two proposals (from Northrop Grumman and Boeing). Both look like the B-2. For the Northrop Grumman proposal, the main difference is that the stubby wings are "cranked" (moved forward a bit, rather than continuing in a straight line from the body of the aircraft).
These derivative designs were apparently favored because the air force knew it was unlikely to get the money for a radical (and expensive) new design. Now they've been told they won't even get money for a "B-2 Lite." There was also talk of building the B-3 so it could operate with, or without, a crew. The air force had rejected suggestions that the B-3 be a UAV. But now it looks like that may change, as a B-3 UAV would be cheaper, and a future project more likely to get funded.
The air force hoped to get the B-3 into service in by 2018. That is no longer possible, even though the air force has already spent several billion dollars of its money on B-3 development. All is not lost. The B-3 spec called for a smaller and stealthier aircraft that carried a ten ton bomb load (less than half what current heavy bombers haul). This recognizes the efficiency of smart bombs, which are more than a hundred times more effective than unguided bombs.
Meanwhile, the most cost-effective bombers continue to be the half century old B-52s, simply because they are cheaper to operate. The well maintained B-52s are quite sturdy and have, on average, only 16,000 flying hours on them. The air force estimates that the B-52s won't become un-maintainable until they reach 28,000 flight hours. Thus these aircraft could serve another 20 or more years. The B-1 and B-2 were meant to provide a high tech (and much more expensive) replacement for the B-52, but the end of the Cold War made that impractical. The kinds of anti-aircraft threats the B-1 and B-2 were designed to deal with never materialized. This left the B-52 as the most cost effective way to deliver bombs. The B-1s and B-2s are getting some of the same weapons carrying and communications upgrades as the B-52, if only because these more modern aircraft provide a more expensive backup for the B-52.
In the last half century, the air force has developed six heavy bombers (the 240 ton B-52 in 1955, the 74 ton B-58 in 1960, the 47 ton FB-111 in 1969, the 260 ton B-70 in the 1960s, the 236 ton B-1 in 1985, and the 181 ton B-2 in 1992.) All of these were developed primarily to deliver nuclear weapons (bombs or missiles), but have proved more useful dropping non-nuclear bombs. Only the B-70 was cancelled before being deployed. The B-1 was delayed and almost cancelled, but proved that the air force would do anything to keep the heavy bombers coming.
The way this is going, it's likely that the next heavy bomber will be smaller (60-100 tons) subsonic, stealthy, uninhabited and familiar looking. The air force will probably have to propose a substantially cheaper aircraft as well, if they ever want to get Department of Defense backing for a new heavy bomber. In any event, initial plans for the B-3 called for heavy use of breakthrough (not invented yet) technologies, and getting the wonder bird into service sometime in the 2020s. That was quickly dropped when the cost of the B-2 (two billion dollars per aircraft) became another media feeding frenzy. The B-3 will have to be cheaper, and one way to achieve that will be to dispense with the crew. It will be interesting to see how this plays out.