Hello to everybody and especially all the contributors!
I can happily announce that the first pull request has been created: https://github.com/joomla/joomla-cms/pull/3759
This PR introduces a large chunk of tests to document the current behavior of the core router classes and is the foundation to rewrite the system in a backwards compatible way.
In the future, I will keep you all posted on the progress of this effort here on this site. Considering the timetable: I'm lacking a bit behind, but all major roadblocks should be gone now and I should be able to devote most of my time to this project.