Producer Kensuke Tanabe believes there is room for more Metroid Prime titles. http://www.nintendoworldreport.com/newsArt.cfm?artid=20349 In an interview with Official Nintendo Magazine, Nintendo producer Kensuke Tanabe, producer of overseas titles like Punch-Out!! and Excitebots, mentioned that there is room for one more Metroid Prime title on the DS.
When asked about the possibilities of the Metroid series he said: "We are always planning to make new games in the Metroid Prime series. Depending on the timing and the situation, we cannot deny the possibility of realising it on DS or DSi."
On the DS, there have been two Metroid Prime titles: Metroid Prime Pinball, a pinball-themed game developed by Fuse Games, and Metroid Prime Hunters, an online-based multiplayer game inspired by the story and gameplay of the Metroid Prime universe. Next year, the newest Metroid console title, Metroid: Other M, will be released, which is not associated with the Prime series.