It seems like a few years ago Next Level Games (Luigi's Mansion 2) wanted to make a new Metroid game. The source of this rumour is concept art from an artist who used to work there, which showed up on Nintendo Online last weekend, and amongst them images is one Samus Aran.
According to multiple sources, Next Level Games made a bare-boned version of Metroid, but Nintendo obviously didn't go for it and Luigi's ghostly adventures were made instead. It's not known what Next Level Games is working on today, and no Metroid has been shown since Metroid: Other M was released four years ago for Wii.
Thanks My Nintendo News