One thing that we are all sure of is the fact that Apple is expected to come up with the iPhone OS 4.0 sometime this summer. There is also the possibility that the company will launch the iPhone 4G in the next few months.
The Interweb is already abuzz with news regarding new features and functionalities that might make their way into the iPhone OS soon. These include new syncing capabilities and the extension of multitouch to hitherto unheard of places in the UI. There is also a talk that other UI enhancements will help the iPhone UI remain "with the times" and not start becoming outdated.
The other thing that is probably getting the most attention is the news that the iPhone OS 4.0 might actually get the much awaited, true multi-tasking abilities. Folks over at AppleInsider are reporting that OS 4.0 WILL come with full support for multitasking. This means you would be able to run multiple third party applications along with Apple's native apps - all simultaneously.