People are really reaching. Here's a fact that will kill any rumor or ridiculous theory...
Three of the last four GTA games have come out less than a year after their debut trailer. The only game that deviated from this tradition was GTA IV, and that was because of the delays. Even then, it still released only 13 months to the day after the first trailer.
Rockstar doesn't like to hype of GTA games for years in advance, probably because they just don't need to. Everything points to this October, unless there is a delay. And I think a delay is unlikely, because I'm sure they've been working on it since GTA IV released four years ago.