Hi and welcome to the forums, i too was new to the forums only yesterday but have replied so many times i'm now a member (wonder how many posts that took)
Anyways regarding the discount for people who are still with the supplier sounds intresting, though when i got my 3G iPhone, was told i could have nearly every phone for free (nokia N95 was £50 at time) but with the iPhone No discounts at all were aloud to be given as this was Apple that enforced this on them.
But now that O2 are no longer exclusive to the UK then maybe their could be some truth to this, hopefully it wouldn't involve the usual retentions/threatening to leave scenario game we normally have to play for discounts.
Also providers will be keen you stay in contract as alot of them, especially O2 have changed their contracts, so less minutes and capped data for same price points, so pretty sure that by dangling a carrot and a £50 or so saving off the cost of hanset by being loyal will get you to stay with them and into the new contracts, forefiting any unlimited data plan you currently get.