A few details about Metroid Prime 3 have been revealed on their official web site. The game is the last of the trilogy and will include updated visuals and more Phazon, the odd material seen in previous installments. Retro Studios does not plan to use a third person camera view when Samus is in the suit (we are not sure if this means that she plans to take the suit off during the course of the game or not). They have also announced that the game will utilize the new features of the Revolution controller.
Keep checking back for more info on the game.