Power will always be commensurate to size. I don't think anyone expects a MW scale laser on an F-35B, considering the available shaft horsepower. The B-1 work might also be construed as a backdoor way to keep B-1R work moving forward.
That said, I wouldn't necessarily say ABL is flat out dead yet. While it is true that many components are specific to a COIL type laser, it doesn't necessarily preclude using it as an airborne testbed for other technologies. Solid state systems are being designed as linearly scalable module sets, so putting many of the same type onboard is doable. But a laser that actually needs the size of a 747 would be a free electron type laser, which if I remember correctly, ONRL is involved with.
Additional power for such systems can be achieved through additional APU arrangements. Boeing has done early work several times on jet engine based APU designs that are podded for command and EWACS aircraft, and can mount on existing engine ferry pylon positions.
Cooling is probably the harder problem. ABL basically dumped laser gases overboard, carrying away heat with it. Anything else needs a substantial cooling arrangement.
