The first unstable build of version 2.2 is available. However, nothing much has changed yet compared to 2.1.
The only major change in this build is that mobj state action functions support Doomsday Script. This represents a step forward in scripting integration, particularly in the game-side objects.
I still have about 600 commits in my work branch pending cleanup and fixes. I've been working on getting rid of Qt dependencies and relying on solely on SDL and other smaller libraries. This is a very disruptive change, though, so getting it merged will require some further work. Even so I would expect the master to de-stabilize further as a result, for a while.