Fez 2 is in development at Polytron, it was just announced during the Horizon indie game press conference at E3 2013.
The developers didn't release any details about the game, just showing the logo for the in-development title followed by an image of the company logo.
Shortly after announcing the game at Horizon, Polytron posted the video below on their website as their Fez 2 in a post labeled "announ-cement". According to the video description, the game is being created by Polytron and musician Disasterpeace and is "coming to ???? in ????"
Announced in 2007 and released in 2012, the original Fez is a highly stylized 2D platformer set in a 3D world. The game won a number of awards including Seamus McNally Grand Prize at the 2012 Independent Games Festival.
We've reached out to Polytron for more information about Fez 2 and will update this story when they respond.