Found this gem of an article.
One of the major questions about the effects of Apple increasing the iPhone’s screen size to 4? was how that would affect the 700K apps on the App Store. Developers had been at turns skittish and confident about how their apps would translate in the weeks leading up to the event.
We reached out to a few active iOS developers to get their thoughts on whether the larger screen would mean delays or a more difficult development process. The general consensus was that it shouldn’t pose too many huge problems, but that it would be a lot easier to test their apps if they had a device in their hands.