The Metroid franchise will return to the Switch very soon, if a new tweet by a credible Nintendo insider is any indication. Along with other information in the same tweet, this could represent Nintendo's release schedule for 2021 starting to fall into place.
The last few years have been a rough time for the Metroid franchise. While Nintendo announced Metroid Prime 4 as one of the Nintendo Switch's first flagship titles, the company later revealed that it had completely restarted development under Retro Studios, the developers of the first three Metroid Prime games. Nintendo has made no official announcements since then, leaving fans uncertain as to the future of the game and the franchise as a whole.
The tweet by @phluttilippe hints at several upcoming Nintendo games, including new Pokemon and Fire Emblem releases. Of particular interest to Metroid fans is the image of Samus, taken from the cover of Metroid 2: Return of Samus. There's no clear indication as to whether the image was chosen specifically to hint something about that game, or if it is interchangeable with any other picture of Samus. Given that Metroid 2 has a Nintendo 3DS remake, Metroid: Samus Returns, it's odd that the tweet didn't use art from that game instead.
There are a couple of major possibilities for what the new game (or games) could be. It's possible that Nintendo will only bring ports of pre-existing Metroid games to the Switch in 2021. Fans have speculated that Nintendo would bring over Metroid: Samus Returns, as a game that came out at the end of the 3DS lifecycle could benefit from a larger audience. Alternatively, rumors suggest that Nintendo has been sitting on a complete Switch port of Metroid Prime Trilogy for years. It would be a no-brainer for Nintendo to finally release it in 2021, if such a port does exist.
The more exciting possibility, of course, is that entirely new Metroid games will arrive this year. The most obvious possibility would be Metroid Prime 4, which has shown signs of rapid development at Retro Studios. Alternately, fans would likely be thrilled by another side-scrolling Metroid in the style of Metroid: Samus Returns. Although unlikely to come true, it's possible that Nintendo could revive development on Metroid Dread, the cancelled follow-up to the beloved Metroid Fusion.
There is another possibility for the year to come that might not be warmly received by fans. Nintendo's new acquisition of Next Level Games guarantees that the subsidiary's attention will be fully dedicated to Nintendo. As the studio made the poorly-received Metroid Prime: Federation Force for the 3DS, Next Level Games could develop a sequel or remaster. Given the huge financial success of its Luigi's Mansion games, however, Next Level Games probably has better things to work on.