Apple iOS 5 is expected to bring new features including a new notification system. With an iOS 5 announcement expected during the upcoming WWDC 2011 it is no surprise that apple developers are starting to see references to the next version of iOS appearing in statistics all over.
The image above shows some of the devices which will be treated to the update. The iPhone 3GS would probably see the first version of iOS 5 as well, before it is shelved from future updates in favor of the newer devices. These stats would mean that the beta release of iOS 5 is not too far away.