The 5-year agreement for Cingular means no other carrier in the US will be able to sell it until this expires. This has been reported elsewhere , although always with the reservation that it's unofficial (neither Apple nor Cingular want to disclose the terms). RIM can only limit itself here. The more carriers that are offered the more they stand to make off it. I cant imagine apple buffs completely ducking out of a contract with say Verizon (SPRINT, T-MO) to switch to Cingular just for a phone, especially with the great service and/or features of other carriers. And this is the simple and humble point of my post...
Sidenotes:
Apple Deserves a Breakout
RIM Mounts iPhone Defense