Going by Naughty Dogs records its going to be a new IP. We had a potential leak last year on 4Chan/Reddit. It might have something to do with the constant teases of Savage Starlight?
Might contain minor spoilers, if you don't want to read its going to be an FPS and a Steampunk game. Take with grain of salt since this is rumour but apparently its the same source who leaked TLOU 2 release date.