Speaking to Official Nintendo Magazine, Nintendo's Kensuke Tanabe who oversaw the Metroid Prime Series for Nintendo has hinted that there may be more to come from the series, despite Metroid Prime 3 being the last of the trilogy.
"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."
This could explain the "secret" ending in Metroid Prime 3 then, and another DS Metroid is very welcome. Metroid Prime: Hunters was excellent, and had online too, unlike the Gamecube and Wii counterparts.
[URL="http://www.officialnintendomagazine.co.uk/article.php?id=13266"]Source[/URL]
As a Metroid fan, I'm happy to hear the Prime series isn't completely over, and I enjoyed MP Hunters on the DS.