Well I already watched the first season, finished it's OVA last year, and read the manga... But I have heard some rumors of having a season 2 of ONE PUNCH-MAN... Well I don't know if it's true but if it is true when will it be release?
It is not officialy announced . Is too early for it to be released for various reasons.
As noted in Youth Health Mag, the sophomore run of the anime may not be arriving anytime soon since the manga is not even finished yet, which means that there isn't sufficient content to be adapted as of now. "One Punch Man" manga is currently at chapter 86 titled "Garou Arc." It can be remembered that the first season closed with episode 12 wherein Saitama fought with Lord Boros. In manga, it happened around chapter 37. The Bit Bag also noted that it usually takes six to nine months or one to two years to develop a whole new season.
However, there are some hints:
There is some good news for fans of the anime, of course, as creator Murata Yusuke has already informed and promised fans that the team behind the hit anime series is hard at work in coming up with a definitive second season. In fact, if things go well, there would be a pretty good chance that "One Punch Man: Season 2" would be released around November or December, according to Christian Today.