Finally after months of speculations and rumors finally today Apple unveiled iOS 5 for iPhone 4, 3GS, iPod Touch 3G, 4G, iPad 1, 2. iOS 5 final will be released on this fall where as developers can download beta version of iOS 5 to test & make their apps compatible with iOS 5 today itself.
Developers registered with Apple Developer program can head over to iPhone Dev Center to download iOS 5 Beta. Keep in mind that only develoeprs or users who has UUID registered can install iOS 5 beta. Also if you rely in unlock or jailbreak then as any cost dont upgrade to iOS 5 betas. You can read about complete iOS 5 features list.