According to Apple Insider, iPhone OS 4.0 will be officially supporting Multitasking feature. You won't be needing to Jailbreak your iPhone to add multitasking feature to your iPhone. iPhone firmware 3.x is also capable of multitasking but this feature has been restricted by Apple in the said firmware mainly because of security and battery life issues. The current security model of iPhone will close any app you are running on your iPhone as soon as you press the home button which reduces the risk for spyware, adware and viruses.
iPhone Firmware 3.x itself provides multitasking for stock apps like Mail, iPod which keeps running in the background while you can browse the web, and do some other work. But you cant do the same with all iPhone apps. You must Jailbreak your iPhone in-order to run more than one app in parallel using apps like Multifl0w enables true multitasking on both iPhone and iPod touch. However Apple have plans to silence iPhone critiques this summer who loves to praise the rival Google's Android for its superiority in multitasking support.
Moreover with the new tap gestures revealed by iPhone SDK 3.2 Beta 4, there is a possibility that Apple will be going to add new powers to the home screen button in order to support multitasking. Pressing and holding it for some time (Long Press Gesture), for example, could bring up an app switcher of some sort.
Next-gen iPhone 4G is expected to be released at WDDC, 2010. It will have a fast processor, a 5 megapixel camera with LED flash, support for WiFi-N standard, Super AMOLED screen, video chat capability and so on. For complete rumor list of iPhone-4G, please visit here. You might also like to view