Next proper Metroid Prime "would likely now be on NX"
http://www.eurogamer.net/articles/2015-06-17-next-proper-metroid-prime-would-likely-now-be-on-nx
Speaking to Eurogamer at E3, Metroid Prime series producer Kensuke Tanabe
said that due to the amount of content such a game would require, it would
probably take several years to develop.
"If we started for Wii U now, it would likely take three years or so. So it would
likely now be on Nintendo's NX console," he said.
"It's a long time but it would need to include a lot of content, which would take
a lot of work on the development side."
メトロイドプライムシリーズのプロデューサー田邊賢輔がEurogamerのインタビューに答えた
「（本物の）メトロイドプライムは中身を作りこむ必要がある、
今からWiiU向けに作ったとしても3年はかかり、出すとしたらNXになりそうだ」
つまりNXは据え置き確定ということ