I'd push Metroid till next year. Same with Galaxy to be hones. Everyone knows that the most anticipated game of the year besides Halo 3 is Super Smash Brothers Brawl and it needs to come out to further solidfy Nintendo's position right now. I said bring out Brawl around Holiday Season 07. Then you put out Metriod Prime April of next year. Then you bring in Super Mario Galaxy in the Summer of 08.
However this is really dependent on the games Nintendo has coming out. Something tells me that more great titles will come out so its possible for them to release them all in 2007 and still do very well.