Do we even have a reliable source on this?
These "waves" of invites don't make a whole lot of sense right now, considering as far as anyone knows, the Beta isn't even live. "Waves" of invites makes sense when you are trying to make sure everyone can download a client, or trying to ensure that everyone can log in to a live game without a thousand people trying to hit the server at the same time.. but there's almost no reason for invites to happen in "waves" when we don't even know if Alpha is over, or even begun for that matter.
Of course, perhaps the client is available for download and none but the invitees know about it. Though if that were the case, I think we'd have a lot more leaked information (all over the web in unregulated areas like blogs, I don't mean on ZAM)... right now, we basically have nothing but guessing games.
FFXIV: Here's to the future ...