User blog comment:Dorito-god/2 New Artworks Revealed/@comment-4547278-20130417172547

Rockstar said this alongside the release:

"Of course many other modes of transport will also be available to accomodate your travel needs across Los Santos and Blaine County on September 17th..."

This means 2 things.

1. Blaine County must be the new name for Red County and/or Whetstone.

2. September 17th is probably a solid release date. (Nudge nudge Tony...)