I had to talk with a VZW rep today as well. I had some questions about my account and then I turned my attention to the S3. He said in his information the release date was showing
July 9th. I asked about the June 28th thing. He said it didn't matter if you pre-ordered a phone, it's based on when the phone is activated. So, even if you pre-order it, the S3 will not be released until July 9th, so activation will have to be July 9th or after and that will cause that phone to move to the new shared plan. Of course on my account I have 5 phones and two of those are non-data phones. So, he said I could upgrade one of those and then immediately move it over to my line and not lose unlimited data.