What is the main bottleneck here? Time? Or funding?
ros_control is a prime candidate for funding from the ROSIN project.
If there are users / maintainers interested in putting together a proposal and getting (part of) their time funded through ROSIN that would have a high chance of being granted.
Seeing the interest in ros_control expressed by the contributors to this thread, perhaps a small team could be put together to work on a ROS 2 implementation?