I'm finishing up a 3 year contract which is still a really good deal. If I buy an unlocked phone at full price (an iPhone from the Apple Store to be specific) can I just put in my current Telus SIM card and stay on my current plan indefinitely?
The unlocked phone should work fine, and I won't be forced sign on to a new contract when my current one ends, will I?
When the plan ends, nothing will change. You'll be on month to month with the same rates and features. If you swap your phone for an unlocked one, just put your SIM in the new one and go for it. No changes need to happen and Telus won't have a problem with it. I've done it. I switched from the iPhone from Telus to new unlocked phone and it simply just worked. Only hurdle may be if you need a different sized SIM card for the new phone.
Once your contract ends, neither party is subject to its conditions. However, historically, Telus has continued to apply the terms of a service contract you have entered into until you change or cancel it. As such, you can indeed purchase an iPhone from Apple, and insert your current SIM and continue with your current plan. Should your current SIM not fit the new phone, you can obtain a new SIM from Telus for a small fee, and transfer your current plan to it in the 'My Account' section of the website.