To be clear:
Gunn is still directing Superman 2.
Gunn and Safran's producing deal is still active - they still are involved with anything like Gorilla Grodd that they were signed to.
Gunn and Safran can still pitch new shows / movies to DC's new leadership, whether to produce or direct, and that leadership _could_ (but won't) pick up any of their projects.
In reality, Gunn will likely be working on Guardians of the Galaxy 4 as soon as Superman 2 is finished.