No date announced yet. The new PV is here. The big news is that J.C. Staff is going to be producing season 3 (same as season 2). Check out the ANN article for additional staff information. Synopsis of the first season from AniList:

Saitama has a rather peculiar hobby, being a superhero, but despite his heroic deeds and superhuman abilities, a shadow looms over his life. He’s become much too powerful, to the point that every opponent ends up defeated with a single punch.

The lack of challenge has driven him into a state of apathy, as he watches his life pass by having lost all enthusiasm, at least until he’s unwillingly thrust in the role of being a mentor to the young and revenge-driven Genos.