Until Telus or Bell or any other carrier announces the 9800, they have no real reason to reveal a release date and slow down their current sales while everyone waits for it. The moment the other carriers announce the 9800, then Rogers will have to make a move to prevent people from switching.
They're probably not too worried about people going south and picking up phones, as those people obviously won't be porting their numbers over to AT&T. A lot of them are probably locked in their contracts anyways. Rogers, or any other carrier, does not make the bulk of their money from selling the devices themselves.