I have an update! Now that AARGM is poised to enter production, the Navy is looking at "kinematic improvements" to Harm - ie more speed and range - to reduce time-to-target and increase stand-off for survivability. The Office of Naval Research has been funded to work on an advanced solid-rocket motor. Also, the Navy tells me, the Aerojet VFDR rocket-ramjet from the HSAD demo is still a candidate for a future Harm upgrade.
Meanwhile...two weeks ago the Air Force and Navy began talks to define joint requirements for JDRADM, with the intent of fielding a dual-role air-to-air/anti-radar missile by 2022 that can be carried internally in the F-35. The F-35 can only carry two AIM-120s internally, and no AGM-88s, so they need a weapon that can do both. Meanwhile, they have a scheme to pack 6 AMRAAM-sized missiles (total) into the F-35's weapons bays.