Now rumors of this have been going around for a while, but I've been hearing more and more about it, both on the net, and from people in the industry.  Now this:

http://gadgetnorth.newsvine.com/_news/2008/07/14/1663037-telus-to-jump-to-gsm

Although not official, with Rogers selling iPhones like crazy, Telus will almost certainly make the move to GSM.