I have a few sound theories about what year San Andreas will occur in, and a few other fun recurring things from the original game.
First off, on one of the new teaser sites (Cluckin Bell) there is a notice about a law suit that took place in 1994. Meaning that San Andreas will take place in either '95 or '96. In accordance with the Darius Fontaine Online Diagnosis-thingie, I am guessing '96, as that's when the internet started. But I could be wrong on that one. It did state early nineties after all.
On the other teaser site (Epsilon Program) we learn of some mysterious cult chanting Kifflom. Gouranga anyone? For those who played the original Grand Theft Auto, you might remember the Hare Krishna-like sect wandering the streets, and if you managed to hit them all in a row with your vehicle, you got the Gouranga Bonus
Of course, I might be mistaken.