Today Nintendo announced that Metroid Prime 4 is restarting development under a new developer and will not be releasing any time soon. They claim that the game under its original developer was not coming together in a way that Nintendo was happy with releasing. I don't think Nintendo ever actually said officially who was working on it before but all rumours point to BANDAI NAMCO Studios Singapore Pte. Ltd..
The game is now in the hands of Retro Studios best known for creating the original Metroid Prime games back in the day. Do keep in mind that the creative leads (and founders of Retro Studios) did leave the company after Metroid Prime 3: Corruption released and founded Armature Studio.
What this means for the rumoured Star Fox racing game is yet to be seen. Nintendo also said that it will be awhile until any new information on Metroid Prime 4 is given.