You realize that once you no longer have a contract, neither party is subject to the terms of that contract? You can walk away at any time, and they can change the terms and rates at any time upon 30 days notice.
Just like with any other service, the rates can increase. Netflix is a great example of this, with the rates changing quite a bit over the past few years. Telus knows you won't find service for $35 anywhere else and depending on what you have for a plan, probably not for $50 as a new customer.