We finally have have had new details on Metroid Prime 4 a few months ago, along with what to expect in it. At this rate it is looking to be the last Switch game ever, uncertain it is right now though on if the game will be Switch exclusive or doing what had been done with Twilight Princess and Breath Of The Wild. Considering the amount of time Retro Studios spent working on Metroid Prime 4 after taking over it's development, I don't see it being the start of a new trilogy, instead it should be something which can confirm where in the series timeline it falls under. I mean it could be a separate timeline from the other games, or it could take place before the events of Metroid II: The Return Of Samus, if it's the latter then Metroid Prime 4 should have an ending that ties into the events of the Game Boy game I'm referring to. Once we learn more about Sylux, we could even find out as to why he never showed up in any 2D Metroid games or Metroid Other M, though to be fair another certain character from the Metroid Prime series didn't show up in those games either, in fact it's uncertain on what became of Dark Samus since the events of Metroid Prime 3. Other ways the timeline placement of the Metroid Prime series can be confirmed is by not featuring what Samus first became capable of in 2D Metroid games and Other M which came take place after The Return Of Samus, in addition to featuring Planet Zebes still standing.