We haven’t done any of the work to create a generic shim yet; the PR link I posted was thoughts on designs and how to ease transition from ROS1 to ROS2. We have a few of the parts in place, but not the bulk of it. We will be doing more work on this in the future to make it easier to port.
If you want to port the kinect2 driver to ROS2 right now, I think you’d have to make a new branch/fork, and do the changes in the separate branch. If you want some ideas on the kinds of things you would have to do, you can look at the https://github.com/ros2/ros_astra_camera driver that we did.