It seems like it was only last year when Koei Tecmo partnered with Nintendo to launch Hyrule Warriors for the Wii U. The Dynasty Warriors and The Legend of Zelda crossover was wildly successful, with over 1.2 million units sold according to VGChartz. In addition to these sales numbers, Koei Tecmo cited Hyrule Warriors as breathing fresh air into the Warriors series, saving it from declining sales. It's no wonder then that Koei Tecmo would want to try to recapture this success for a second time. Recent rumors have indicated that the developer is already hard at work on a new Nintendo-themed Warriors title. The rumors don't indicate anything about which of Nintendo's IP would be used in the crossover, with the exception that it's neither The Legend of Zelda nor Star Fox.
I strongly believe that the Metroid universe would be a great addition to the Warriors series. Head inside to see why I think Metroid Warriors should be Koei Tecmo and Nintendo's next partnership.