Yes, if this trend continues Apple will fragment iPhone OS devices once every 3 years. Awful when you consider that Android is fragmenting every month with the introduction of yet another device.
You can buy an iPhone 3G today from Apple that does not support all the features in OS 4 that comes out next month.
"iPhone OS 4 will work with iPhone 3G, iPhone 3GS, and the second- and third-generation iPod touch this summer, and with iPad in the fall. Not all features are compatible with all devices."
Also, if the new iPhone does have a higher-rez screen, there is going to be even more fragmentation.
Not that this is awful or the end of the world, but Apple isn't magically exempt from these things.
But realistically it's much less of a problem in that ecosystem. And if you write for the 3G, it will work on the OS 4 devices. It's only an issue if your app needs the bleeding edge features or speed/mem.
I agree with what you said here, and upvoted, but I'm not sure that it's a correct statement. What appears to be the case is that iPhone OS devices will be considered software-obsolete in the third year of availability, if we're extrapolating the trend from the limited data we have.
That is, I fully expect that my iPhone 3G will not run iPhone OS 5 and that the iPhone 3GS will not run iPhone OS 6 (or whatever number they're up to in two years). It's still a solid story for iPhone OS development compared to other handsets.
It appears to be one of the lessons that Apple took to heart from the PalmOS example (they were at 160x160 for years, then 320x320 and only a few folks took it beyond that).
