Guild beta just began last week, which according to Mythic, is the last phase of closed beta. Assuming that they will need at least a month with the guild testers, and barring any major bugs or issues i would say end of August early September. This of course is all pure speculation on my part.
Keep in mind that the dates you are seeing on the retail sites (for a release date) are merely an educated guess as to when they think the game will come out. 2 months i think would be highly optimistic. 3 would be more realistic and 4 would be the safe bet. And that is all assuming that they don't find any game breaking bugs or issues.
Speculating on release dates has become sort of a sport in the MMO community, and it is perhaps the most futile endeavor. The only people who have any idea are Mythic employees and I would put big money on them not talking.
Anyway, the best anyone can tell you is... patience is a virtue, specially when dealing with beta phases and release dates. I know that doesn't help you much, but its the best answer you will get outside of bugging Mark Jacobs' office, which I am fairly sure would get you banned from beta.