Apple does not accept app’s from developers which do not support their older model, the iPhone 4.
Unfortunately they decided to change the screen ratio, so your left with either stretching your game or repositioning your interface elements.
(the black bar solution is not longer accepted)
It makes sense to support the device since a lot of people still use the 640*960 screen ratio generation.
But for developer it means basically go through your whole app once more and get sure everything sit’s correctly and is not cut off or stretched.
For the iPhone 4 optimizations I roughly estimated 16 hours of work ahead. 🙂 What ever, music turned on and go.