Maybe I'm not clear on the conditions, but I am currently eligible for an upgrade and did a week trial of the Samsung just to try it out before deciding on waiting for the 5S. And when I did the trial, it was basically like getting a new phone. I had to pay for it and renew my contract. So my new upgrade date became 18 months from when I started the trial, but it was still a 2 year contract. The upgrade date reverted back when I ended the trial and decided not to stick with the Samsung. Got my refund, the whole 9 yards.
Might be because I've been a Verizon customer for years. But if the conditions did change, oh well!