http://www.tvguide.com/News/New-Girl-Season-4-Spoilers-Jess-Nick-1084685.aspx

"It's been easier for me to just write them as single people, single idiots (who are) kind of out in the world trying to get laid and looking for love,” says Liz Meriwether. "It's just been more fun. I had trouble kind of figuring out where the conflict and the comedy was coming from in their relationship last season.”
Read more at http://www.hitfix.com/tv-tattle#seYyTov7QCkXkSho.99

I was wondering if they add one more guy and one more gal in this show's main cast to make it eight.

There will be three women and five men in this cast.