There is no guaranty Manning will be the player he once was, but if you bring Manning in you could sell out probably every home game. Jersey sales would skyrocket. The Miami Dolphins would have a new face to the franchise and we would have numerous prime time games. W are not talking about just any QB....this is one of the best QB's to ever play the game.
I would rather take the risk that Manning still has some very good years left in him, and he could attract other great players here....guys like Dallas Clark and Reggie Wayne from the Colts, just for starters. Miami always seems to want to play things too safe, and we never get anywhere by doing this. I think a GM /Owner would be crazy to pass on P. Manning.