The rumors floating around the internet are true: Bandai Namco is handling the development of Metroid Prime 4 for Nintendo Switch. The game was announced during Nintendo's E3 2017 broadcast, but at the time, Nintendo noted that Metroid Prime series developer Retro Studios was not handling the title.
Eurogamer is reporting that multiple sources have confirmed that Bandai Namco Singapore is developing Metroid Prime 4 in collaboration with Nintendo. The studio is comprised of former LucasArts Singapore staff who worked on projects like Star Wars 1313.
The rumor mill started when folks online began looking at the LinkedIn profiles for Bandai Namco Singapore developers, noting that one profile mentioned work on a "first-person shooter/adventure exclusive to the Nintendo Switch". This profile also pointed to Ridge Racer 8 as a Nintendo Switch exclusive.
The Eurogamer report says the game is still relatively early in terms of development. It's looking unlikely that it will come out in 2018.