I just called Gamestop, they said it will be release April 2, 2011.
I wouldn't put too much faith in this. why would gamestop know the release date before Sony?
Well all I know according to Best Buy, is it's on backorder for one to two weeks. So after next week. Lets just check & see what they say after that.
Update, the backorder has been removed. But no best buy has the game yet. I called one near me, they said. there's another best buy showing that they have the game. So called that other store. They said they don't have it yet. Then the guy said, maybe just the preorder came out today. He wasn't to sure about it.
It seems Best Buy has updated their site on ICO & Shadow of the Colossus Collection.