While the details to who voices Gou and other key characters like Sousuke have not been revealed by FUNimation Entertainment those announcements can be expected sometime over the weekend. For now, all the voice actors for the lead swimming boys from Free! have been revealed.
The English Cast for Free! Eternal Summer
Johnny Yong Bosch-Makoto
J. Michael Tatum-Rei
Official FUNIMATION Blog: Free! Eternal Summer Cast-Announcement
All the swimming boys! Now as a fan of Free! one can only expect a priority and immediate release for Free! Eternal Summer in 2015 on home video.