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In the past Apple would begin field testing new iOS versions only after finishing previous versions, which makes sense considering the sequential nature of those versions. The problem is that iOS has rarely been as polished as it should be when compared to hardware releases and so Apple is either shortening its development cycle to have new iOS versions be ready sooner or breaking away from the iOS and iPhone release pairing to make them both independent. Apple also has to worry about how iOS is at the center of so many new products and services, which means that updates have to be tied to their releases as well.
9to5mac.com has published web traffic reports showing that iOS 8.1, 8.2, and 8.3 enabled devices are all surfing their site. This means that all three are being developed simultaneously, which I feel makes sense with a number of other connecting products announced but not yet released. There will likely be an update for the Apple Watch and probably one when Yosemite is finally released. Unless they are going to release every major product for the year on the same day, then iOS development is going to need more flexibility.
The reason for this is that iOS is at the core of the entire ecosystem of products. A few years ago OS X and iOS had nothing to do with each other but now Yosemite and iOS will share quite a lot. You can answer phone calls on your laptop and send text messages, but only when your iPhone is on the same network. The same will be true of the Apple Watch, which will relies on proximity to your iPhone. With the new role of the phone being at the center of so many products, it will need updates more frequently to match nearly every release of other hardware and software offerings.
It is an amazing idea to have so many different devices communicating together but I can only imagine the coding nightmare that Apple is creating for itself. A bug on one platform will essentially be able to affect every device in the chain and cause major headaches. No wonder they are ramping up development on multiple versions at the same time and they had better keep it up.
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