While Apple hasn’t released iOS 4.3 final version as yet, there are already rumors for iOS 5.0 preview scheduled for iPad 2 launch event on March 2, 2011. According to Engadget:

It’s also almost guaranteed that we’ll see the next version of iOS (number 5 in all likelihood, along with its SDK for devs), and an expansion of Apple’s cloud services (that part is a little… foggy right now).

This will also be the perfect setting for Apple iPhone 5 launch, expected in June 2011. We hope we get to see iOS 5.0 preview as soon as Wednesday.

via Engadget