I need a little help here. I'm just curious to know how the phone upgrading works here in Canada, and which carrier provides the easiest and most reasonable phone upgrading system.

Lets say I were to buy the latest Samsung phone a carrier has to offer right now, and then the carrier not too later gets the Galaxy Nexus, which carrier would most likely give me an upgrade option? And would they give me another upgrade if say the Galaxy S III releases just a couple of months after aswell? If so, what are the circumstances and the process? I know my brother miserably failed when he went through an upgrade process with Fido, and I don't really want to end up having to sell my phone, buy the Galaxy Nexus at full price and then hook it up to my current plan. Too much of a hassle and seems to waste alot of money aswell.

Any help here? I would really appreciate it.