The biggest piece of information regarding this rumor is its source -- discovered by newly built fansite Eorzeapedia -- of several Square Enix Europe job listings for new game testers and game masters. The listing is very clear that any applicants are required to have "good knowledge" of Final Fantsy XI, which ostensibly already has these jobs filled. If new people are being hired, it means the more seasoned team are being shifted to the developer's other MMO, namely Final Fantasy XIV. According to those listings, the new game masters begin work in early September.
Loose reasoning? Maybe just a little, but when considering the release date, development time and this new information it all seems to make sense. We'd love to get our hands on some FFXIV beta action any time this year, especially as early as September, so here's hoping it's true!