The hints are rolling in that the iPhone 4G may be launching in either June or July. Starting with the latest, AT&T has blocked employees from taking vacation in the month of June (according to multiple AT&T sources), a month in which employees would normally take for vacation. However the last time AT&T did such a thing was when the older generation iPhone first came out. With that in mind, a June or July period look like a possible release date.
Also, Apple dropped a surprise on the world with their iPhone OS 4.0 software just last week and said the final build of the software will be made public in the summer of 2010. Finally, AT&T CEO Randall Stephenson made the announcement around June last year they were going to end their contract with Apple to offer exclusive service for 3GS and 3G customers in 2010. Apple however wanted to extend the contract process till 2011. This would be a good transition move for Apple. If they were to introduce the 4G during the June/July period, it would be good to phase out the 3GS/3G exclusivity a little bit later in 2010.
So, do you expect the 4G this summer? From these clues it sounds like a very good probability. There are still no real photos of the 4G yet, but hopefully some pop up later on in the year.