First of all, I have a very important question for you. What the hell are you doing reading this while you could be playing Metroid Prime 3: Corruption, the perfection of all that is Wii? Still with me? Right...I guess you're too lame to be playing Corruption.
Anyway, for those who have had the luck of acquiring a copy of Metroid Prime 3: Corruption, I'd like to advise that they check this out for themselves.
Now, to the rumour.

As you can see from the above image, it seems Retro has taken to teasing us about the possibility of a Metroid two-dimensional adventure on the Nintendo DS. Yes, Metroid Dread, which would be the 5th installment on the long-running series (Metroid Prime 1, 2, and 3 are separate, says Nintendo), is apparently nearing completion so that should have it on Nintendo's announcements soon.
Yes, there is the possibility that this was an accidental tease from Retro and it was just meant to tell us about Metroid experiments, but it is not mentioned anywhere else on the game.
Still, take this with a grain of salt. Samus hopefuls should not totally discard the idea of a new 2D Metroid, though, seeing as how Nintendo released Fusion on the Game Boy Advanced. Here's to Metroid Dread *gulp*.