You're probably right. But Marco's argument hinges on the idea that:
- there will be fragmentation
- hence it will be difficult for developers to write apps that make the most of iOS6 and iOS7
- hence this is an opportunity for nimble new players to enter the market and capture the iOS7 userbase
I agree that there probably wont be fragmentation, but the point is, Marco is saying if there was, it will be a brilliant opportunity. Therein lies the mental gymnastics.
I think he's more saying that people will be reluctant and/or unable to completely rethink their apps design and functionality and this will present an opportunity for new developers who build things that are uniquely suited to iOS 7 and beat the old slow-moving incumbents.
"Most [developers] can’t afford to drop support for iOS 6 yet. (Many apps still need to support iOS 5. Some unlucky souls even need to support 4.3.) So they need to design for backwards compatibility, which will be extremely limiting in iOS 7."
- there will be fragmentation
- hence it will be difficult for developers to write apps that make the most of iOS6 and iOS7
- hence this is an opportunity for nimble new players to enter the market and capture the iOS7 userbase
I agree that there probably wont be fragmentation, but the point is, Marco is saying if there was, it will be a brilliant opportunity. Therein lies the mental gymnastics.