I would be surprised if the Blues go along with this. They will probably leave him in college to start next season if Johnson wants to play at this tournament again that bad, then talk contract next January to have him in the NHL for the latter half of 07-08.
The main reason for this, is I don't think the Blues (or any other team) would want to be the team to set this precedent. That, and I don't think John Davidson is the kind of GM to allow a player who has never set foot in the NHL to push him around on his contract.
Could you imagine if Sidney Crosby or Alexander Ovechkin told their agents to get this written into their contract? It wouldn't be pretty. If I'm a Penguins or a Capitals fan, no way would I want to lose Crosby or Ovechkin for a month over Dec/Jan. I would think Blues fans would think the same about Erik Johnson.