How about a bigger screen? 3.5" has been around since 2007. It's old now. 4" would be the best.
How about a faster processor? Yup, we're getting it for the iPhone 5
How about a better antenna? Yup, we're getting it for the iPhone 5
How about better battery life? Yup, we're getting it for the iPhone 5
How about a better design? There have been too many complaints about the iPhone 4 model. Proximity issues, easily broken screen, ergonomic issues, antenna issues, no white model etc.
Software wise:
How about a notification system? We need that, as Android completely dominates in that aspect.
How about some revision for the UI since it's been the same for 4 years?
How about an option to turn Multitasking ON/OFF, and a Kill button to close all apps?