Working!! Season 2 will be airing in Japan beginning October this year, however some TV stations in Japan will preview the first episode on September 3.
A-1 pictures is the studio behind this series and the main seiyuu cast will remain in the anime along with new characters being voiced by Yuuichi Nakamura and Haruka Tomatsu.
A new trailer is also showing on their official website
Update: some kind folk has uploaded on youtube, here is the stream