i still dont think you get it.
its not about launch day phones, its about getting phones more often than every two years.
getting a phone on launch day makes no difference. so what if someone bought a 4s in may of 2012? 24 month upgrade for them isnt any worse than it is for you:
May 2012: 4s
May 2014: 5s
May 2016: 6s
its still a new phone to the person buying it, nobody but the biggest fanboys care about launch day, which is completely irrelevant to the issue at hand.
Of course getting a phone on launch day makes a difference.
If I bought an iPhone 5 in October 2012... why the hell would I even need an early upgrade since the next iPhone Im going to get is in October 2014?
If anything an early upgrade (20 months instead of 24) would fall under July 2014 and do me no good since I'm going to wait for the next iPhone in October (24 months later) anyways.
As for those who's upgrade is later then October well that's just too bad for them and they should have planned better. If anything the early upgrades rewarded people for buying an iPhone late in its life cycle and eventually allowing them to 'catch up' to the release date of the newest model, thereby making it harder for those that were smart about their upgrades to make them in October to obtain an iPhone on launch day.
Now it's simply concrete: Want to buy a phone in May near the end of its life cycle? Fine. Just be prepared to wait until May two years from now and have to get your next iPhone late in its life cycle as well.