With the formal launch of iPhone 3G in the Middle-East later this month, there have been growing rumor about Apple launching the next-gen iPhone as early as this June. AppleInsider has this to say:
The source of the June comment is not entirely clear, but appears to have come by way of Davis. That said, industry watchers generally expect Apple to take the wraps off its next-generation touchscreen handset in June, approximately one year after the iPhone 3G made its debut.
[via - AppleInsider]