Iphone 5 and Iphone 4s both are coming out late Aug/ Sept, Iphone 4d being a cheaper unlocked version. This is pretty much 90% true by now as they are hiring thousands of temporary employees all over during these period. Also, the manufacturing taiwanese company has leaked the fact that it has received a massive order for production (this is prolly because a huge company in China) will start selling the newer versions. There was overheating issues with the newer A5 chip but the issue has been resolved now. However, they wont bring the phone out until they start OS 5 distribution, so my educated guess would be Mid/ Late Sept.

Sources:
Macrumors.com
9to5mac.com
macstories.com
cultofmac.com
appleinsider.com
macrumor.com
techcrunch.com
engadget.com
wired.com

Plus, I'm a HUGE HUGE Steve Jobs Fan. I have every single products apple has ever invented and will prolly buy whatever comes in the future.