Raptors GM Bryan Colangelo knows that Bosh is leaving following this season and there is nothing he can do to prevent that. Losing Bosh with no compensation to free agency is a worst-case scenario so Colangelo should deal Bosh now to maximize his value. If Colangelo wants to save his job he has to deal Bosh this season to minimize the bleeding.
Petrie has accumulated the ammo for a Bosh deal by drafting well and retaining those players to reasonable contracts. The reason why Tyreke Evans, Omri Casspi and Jason Thompson are not included in any potential deal is because Petrie has probably marked them as untouchable franchise cornerstones. This should not be a deal breaker though.
Kevin Martin would be the main attraction to the deal from the Raptors perspective. Martin is an offensive dynamo; capable of averaging 30+ points per game in a fast tempo offensive system like the one the Raptors run. Martin is only 26 and has yet to reach the ceiling of his potential.