No release date announced yet. This was posted to the official twitter account for the show. Check out the Crunchyroll article for additional 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.
IIRC first season was animated by very good animators brought from many studios and freelancers, and the animators had a lot of time to get it done, so even if it was still in madhouse’s hands, they probably wouldn’t be able to match the quality of the first season.
Would still look better than what J. C. Staff will release, though. We’ll see how much, but as someone who doesn’t read manga, ok quality season 3 is better than no season 3.