No, what I'm "afraid" of is someone deciding after 8 months that they want something different so they decide to go back to iOS 6, and then they wonder why the app they were using for the past 8 months doesn't work, or why it's missing features, and so they complain and expect support for said app.
You can question my assumption of 75% all you want, I merely said it was an example of what could happen.
If you would have read my posts, iOS 6 had a 93% adoption rate. Yes that's after all of the iPad ones which couldn't be updated, and the iPhone 3G or whatever other devices lost support in iOS 6. We still had 93% adoption, so don't tell me that 75% is some unheard of number. I'm pretty sure that iOS 7 is already around 75%. So no, I don't think that iOS 8 is going to cause more fragmentation, just like iOS 6 didn't, and just like iOS 7 didn't, because apple doesn't allow people to downgrade. I don't care about your family that has saved your original apple products, the fact is most people are not keeping original iPads, and the ones that are account for a very small percent of the overall market.
Allowing a rollback would change the business model if 25%, 30% of people decided to jump around between iOS versions and expected working apps and continuous support for both. iOS 7 is a complete rewrite, and apps are completely different from those on iOS 6. It would essentially equate to maintaining two separate apps. The fact that you claim to be a software developer and have NO knowledge of the state of iOS, it's adoption rate, and the impact of fragmentation makes me think you really haven't been doing it for 30 years, but hey, I guess it's serving you well to be extremely uneducated in your "30 year business"
Not everything has to do with updating apps. How about a brand new app that I make next year where I may have a divide between iOS versions and I have to decide which version to support or decide to support both (likely hampering the iOS 7 version and removing features and new APIs to dumb it down to iOS 6 standards). You act as if every app for iOS has already been created and the version for previous iOS iterations already exists.