Metroid Prime: Federation Force may point to a Metroid Prime 4

[AZWification]

Luke888 said:
Next Level Games is the logical choice since they worked on Federation Force, if not just them, then possibly them collaborating with some Monolith Soft developers: since Monolith Soft developers are already working on BotW it might be a smart move by Nintendo to stop whatever development is going on at Monolith Soft with the remaining members of the team and make them collaborate with NLG on MP4 at least until BotW is released, an additional say 50 developers for the next 7 months (at least since Zelda isn't confirmed to come out in March) would make them advance A LOT in the development, the title might even be ready 1/2 years afterwards. Once BotW is released all Monolith Soft developers go back to their next RPG which has been worked on since probably May 2015 (month following Xenoblade X's release) at least by a portion of the the team

NLG seems to be the logical choice, in this way Tanabe is still involved in the production of the game. There was a rumor that he wanted Retro to work on Prime 4, but they didn't want to do that so there was a small conflict and now Tanabe is no longer the producer of Retro games. It's just a rumor, but seems likely to me.