Source: Tomodachi 100
According to the Anime Guild Vol. 54 (A special page in the manga focused on the FT anime), the new opening song will be called Fairy Tail ~The Promised Day~ (フェアリーテイル~約束の日~), sung by the person who did RAVE's first opening theme, Yonekura Chihiro. The ending theme will be called We're the Stars, sung by Terakawa Aimi .
Mashima said via Twitter that the new OP forebodes an amazing fate... although "fate" doesn't look so great if we go by the latest chapters :)