For online pre-orders through Apple I believe you can only buy unlocked full price or at least that is how it looks right now.
I am with telus and have put my email address to register for updates as to when their details are available. I am also near the end of a contract and expect telus to send me some sort of offer update.
The last time I upgraded to my current iphone 5 if I recall I did pre-order with telus but cant remember if I was guaranteed delivery by the date of release or not. I know I opted for a later date because I initially ordered a 16gb model but they offered me a upgrade to a 32gb if I waited a couple weeks after the launch date, not a bad deal.