I'm from the bomb squad. If you see me running, you should too.
Bungie DID say we aren't playing as chief anymore, and they tend to keep to what they say. From what little we know about the game right now, anything is possible. It seems more probable(and suitable) that it's a prequel, but you never know. in any case, I'm getting out of the forums because all I'm doing is getting frustrated about not knowing about halo: reach and anticipating more information, then having a nervous breakdown where my head a splodes.