I don't think they have released any info yet. I'm sure as it gets closer to June you will begin to hear more and more about it. I'm thinking they may have a strictly iPhone plan with Cingular to put the phone to its full capabilities. That would be ideal in my opinion.
I'd ask cingular how much it is to break a contract. There hasn't been any information released on the cost without a contract either. That is something I'm sure many people are wondering.