A recent eWeek article
states that Apple will not limit VoIP on the iPhone while the phone is connected to a Wi-Fi access point. During a a Q&A session after the SDK announcement on Thursday Steve Jobs said, "We'll limit [VOIP applications] over the cellular network." He went on to say that Apple would not be opposed to VOIP apps that work on a Wi-Fi connection, which is welcome news to AT&T we are sure.
According to the article, SightSpeed is at least one VoIP provider that is lined up to make a VoIP solution for the iPhone. Of course, the big question is: will we see Skype on our iPhones come June (the smart money is on yes)?