There is a rumor that the 4.0 version OS for the iPhone will support multi tasking. There is similiar milti tasking currently on the iPhone, but currently it requires one to close the running app to open up another.

It is said that it will look like the Apple's desktop Expose with icons at the bottom for quick switching in between apps. Hitting the home button twice will pop up the expose feature. When a selection is made, Expose will zoom out and open up the new application. A faster and truer way of multitasking for the iPhone.

Though it is still a rumor, it would be nice to see an update like this out.