Re: Fragmentation
In case you haven't noticed, they stopped supporting older devices quite a while ago, but as they're supporting devices up to three years old, I'm not sure how far back you would expect them to go anyway.
I have no idea how many pre-3GS devices are still out there being used, but how many HTC Dream/T-Mobile G1 phones are still being used today? (They would be around the same age as the next oldest iPhone, the 3G.)
Any news on ICS availability for the original Droid (about the same age as the 3GS)?
Don't forget, these announcements are from a DEVELOPER conference, fragmentation is likely to be a significant headache for quite a few of them and Apple's ability to move 80% of their user base onto the latest OS in such a short space of time is not to be scoffed at; most other vendors dream of being able to do that (esp. Microsoft).
But of course you are correct, the iOS space is already getting quite fragmented with it's one release of OS and four screen resolutions you need to target to hit 80% of the users.
It's barely any better than the Android space where you have a choice of 12 screen resolutions from the current HTC range alone. Not.
For some developers this will be no problem, but for others it will be a nightmare.