I believe the super-dense pixels in the Retina display of the forthcoming iPhone are going to have an interesting effect on iPhone developers. While most are probably chomping at the bit to get new hardware anyway, we’re back to the landscape of the original iPhone release: if you want to see how your app really works, you’ve got to buy a new iPhone.
When the iPod touch was released, it created a relatively inexpensive way for developers to purchase units to test on – no more relying on the simulator. Android developers are still waiting for an equivalent to the iPod touch from a development perspective on their platform.
The new iPhone’s display is so radically different than the current crop of iPhone and iPod touch devices that I’ll wager you can’t get the full experience of the Retina display unless you actually have the hardware.
I’m very interested to see how this will manifest itself in the new crop of apps that will be released in the coming months. I don’t think it will affect mobile web application developers too much, but I’m curious to see what we can do with the new toys as well.