Apple's app ecosystem is a big money maker. In January, Apple revealed that customers spent more than $10 billion on the App Store in 2013, and that developers had earned $15 billion.
And with iOS8 expected to pave the way for Apple's ecosystem to grow beyond mobile devices, developers see another huge opportunity.
One of the most significant features of the new operating system is app extensions, which are basically a way for third-party applications to talk to each other. Extensions make it possible for third-party apps to work with things such as Apple's new Homekit app, which is for managing technology in the home, and HealthKit, which is for managing wearables and healthcare.
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Essentially, the new extensions are Apple's way of getting developers to begin building apps for devices beyond the iPhone.
It's the company's push into the so-called "Internet of Things," said Matt Johnston, chief strategy officer at Applause, a company that tests apps. But building for new platforms presents difficulties, he added.
"The short answer is it's a big headache, but there's also a lot of opportunities that come with it," Johnston said. "Developers are no longer testing their application in a silo, but they are having to test their application and how it interacts with this TV and other third-party apps."
"Testing is going to get a lot more complex because there is a new set of challenges to launch these native experiences," he added.
The fact that Apple is reportedly releasing two new iPhones of different sizes would also make development more challenging, said Ashish Toshniwal, CEO of Y Media Labs, a firm that builds iPhone and Android apps for large companies, including eBay and Lonely Planet.
Two new devices of different sizes means developers will have to design their app for each phone.
While Apple offers developers tools in iOS8 like its unified storyboard feature, which helps developers build apps for multiple form factors at the same time, it's still not a perfect solution, Johnston said.
"Anyone who has launched software knows these things may work in lab testing, but they could fall apart once they're in the user's hands," Johnston said.
And that's a developer's biggest fear, he added.