What I'm interested in is where the next public packet will be, relative to that. I imagine it'll be a few steps ahead of the rules they're playing in the livestream, but still quite a ways behind the internal versions of today.
Well, their big claim on the page for Ghosts of Dragonspear Castle was that it came with the "most current" version of the rules. I suspect that the rules in Ghosts of Dragonspear will become the new public playtest rules and will be released nearly simultaneously online.
That way people who aren't going to GenCon and can't buy the book won't be annoyed and complain about how you had to pay $30 in order to get the most up to date rules. Also, they can't release a newer version of the rules online for playtest because that'll annoy all the people who paid $30 to get the most up to date version of the rules.
In fact, if I was to wager, not only will the next version of the playtest rules come out right before GenCon and will be in sync with those printed in the book. But I suspect that's the last playtest we'll see for a LONG time. Probably at least the rest of the year. Possibly the last playtest we see ever.
I know WOTC pretty well, and unless I miss my guess, they've pretty much got the idea of where they are going with the game and no longer need feedback from the players. Plus, they are paranoid about piracy and likely don't want to print a playtest that contains rules TOO close to the ones they actually intend to publish because it might be too easy for someone to manually edit the playtest document to be the same as the published version.
So, they'll publish the "current" rules in a special edition book for GenCon and then likely not release another playtest at all. Possibly because they plan on announcing a release date sometime soon.