Just going to quote myself from a previous post:

There's definitely room for bias in the stats I've seen but virtually everyone reports almost no iOS 4 devices.

http://stats.unity3d.com/mobile/index-ios.html (Below iOS 5/Other: 1.2%) http://david-smith.org/iosversionstats/ (4.3: 1.6%) https://mixpanel.com/trends/#report/ios_frag