As per the topic title, I believe with the model that Apple has chosen with respect to how they release platforms, the traditional style of support multiple OS versions is not the trend.
With every release of iOS, you see a quick adoption of the new version. You can Google and see the previous histories. Here's a link about the latest iOS 7.1 that was released.
With this information, would you even bother support iOS 6? Probably not. Also, if there is an iOS 6 user, they would be able to purchase the previous supported version, which I hope is of good quality. I would suggest to move on to the newer libraries and upgrade you app for just the main platform. It'll keep your code simple, maintainable and helps keep your sanity. :-)
It's interesting that some companies have old mandates that suggest to keep supporting older iOS platforms. This confuses me since Apple released these statistics. I'm actively sharing and pushing to not bother with older versions. Is that < 20% corporate users? I doubt it. Push for change if you're in a corporation!
Ohhhh tricky topic. Not necessarily part of the original blog, but good to reflect.
BRB!