User blog comment:B214/Don't ask about season 4/@comment-26402117-20160527154931

Thank you for making this blog. It is logical that if the second season came 2013 and the third season came 2015, the fourth season would air in 2017. Basic math, basic logic.

This is an ecchi series. It was unlikely to get an anime in the first place, let alone get a new season every year. The honest reality is that people in Japan don't casually buy this stuff as its not mainstream. So its less likely to make money and thus more of a risk.