it looks like The Epsilon Programme (mentioned in San Andreas) will be mentioned or have a mission centered around it:
Rockstar's first GTA V viral marketing campaign has begun, starting with a number of tweets from the previously dormant Epsilon Program.
The Epsilon Program first made an appearance in GTA San Andreas and has been mentioned numerous times on radio stations and by pedestrians. The religious cult brainwashes it's followers into handing over large amounts of money and is believed to be a parody of the infamous Church of Scientology."
Here's some more information:
"General
•Grand Theft Auto V is being developed by Scotland-based Rockstar North (the same studio that made the previous games) and will be published by Rockstar Games.
•The game will be released in 2012 or 2013.
There is emphasis on the recession.
Story
•The man narrating the trailer is a main character. He moved to Los Santos in search of a better life, looking to put his criminal past behind him.
•The game focuses on the pursuit of the almighty dollar in a re-imagined, present-day Southern California. Money is a major theme.
Setting
•The game is set in Los Santos (Rockstar's take on Los Angeles, California) and surrounding hills, countryside and beaches.
•The game takes place in the present day (i.e. 2012/2013).
•Many cities and districts in Los Angeles County have been recreated in GTAV. These include, but are not limited to: Hollywood (Vinewood), Downtown Los Angeles (Downtown Los Santos), Koreatown (Little Seoul), Venice (Vespucci) and Santa Monica.
Characters
•The old guy who features prominently in the trailer is voiced by actor Ned Luke.
Gameplay
•For the first time in the series, animals feature as part of the game world. Dogs are confirmed.
•Enterable nightclubs (with bouncers) are in the game.
•A blimp (airship) is visible on the Los Santos skyline, near the downtown area, similar to the one featured in GTA: Vice City.
Missions
•One mission involves robbing a high-end jewellery store in the GTAV equivalent of Rodeo Drive (in Beverly Hills).
The crop duster returns to the series.
Vehicles
•Unlike previous games, cargo space can be used to seat characters - it is no longer just empty space.
•Convertible cars with functional roofs are confirmed.
•Jet-skis are among the new vehicles to feature in GTAV.
•Several aircraft can be flown, including helicopters, sea planes, crop dusters, private jets and military jets.
•Huge semi-trailer trucks can be driven, just like those featured in GTA: San Andreas.
Weapons
•There is a strong possibility that weapons can be customized. In the debut trailer, three (silenced) AK-47s are shown with minor differences between them.
Multiplayer
•Like Max Payne 3, GTAV multiplayer will feature "Crews". Join a team game with a fellow Crew member and you'll start receiving bonus XP for select, mutually-beneficial actions, such as rescuing them from near death or assisting them with a kill.
Soundtrack
•The 1968 track Ogdens' Nut Gone Flake, by the British band Small Faces, will feature on the in-game radio.
Technology
•GTA 5 runs on the latest version of Rockstar's proprietary game engine, RAGE (Rockstar Advanced Game Engine), allowing for an unprecedented level of realism and interactivity.
•Like most of Rockstar's recent titles, GTAV uses Natural Motion's Euphoria character behaviour system. Animations are created on the fly and depend on the specific situation that the character finds himself in. As such, each player's experience is unique.
•Sky effects in GTA V are the most realistic we have seen yet in the series. There are several layers of (different types of) clouds, with each layer behaving differently. Clouds also have shadows."
here's some Characters which have been confirmed or will make an appearence:
"Mitch Hayes - 38 yrs old - Annoying, wise cracking, highly successful FBI agent. In great shape. Does triathlons, drinks low cal beer, but still has a sense of humor.
Miguel Gonzalez - 25 yrs old - Young Mexican American FBI agent, caught between a few mob bosses. Very clean cut.
Clyde - 23 yrs old - Moronic, almost inbred and creepy white trash hillbilly. Very naive but in a creepy 'it's only incest sort of way'
Brother Adam - 50 yrs old - Welsh monk, cult leader, yoga teacher, very lithe, very into exploring your personal tension through gripping massage. Needs Welsh accent.
Mrs Avery - 48 yrs old - Neurotic soccer mom, home maker, anxious and addled on pain killers. Very angry at neighbor MRS Bell.
Mrs Bell - 45 yrs old - Swinger, and mellow Californian divorcee. Ugly but comfortable with self.
Eddie - 47 yrs old - Weed evangelist, guy who started smoking at 30, and is now a leading proponent of marijuana's fantastic properties. White, awkward.
Ira Bernstein - 56 yrs old - publicist for an actress known as America's newest sweetheart who just so happens to love animals, orphans, drugs and sex. He's always trying to hide her latest indiscretion.
Kevin De Silva - 18 yrs old - Albert's fat, FPS playing gamer son. Smokes a lot of weed, has anxiety issues and a card for a bad back, very soft, very opinionated. Into making racist comments while playing online.
Harut Vartanyan - 42-52 yrs old - Armenian car dealer, moneylender, would be Fagin and would be bully. Heavily connected to the underworld, but irritates people so much no one likes him.
Nervous Jerry - 48 yrs old - paranoiac living in the sticks, near Simon, completely paranoid, and terrified of Simon.
Calvin North - 55 yrs old - clapped out FBI agent who now mostly works offering advice on TV shows - whose only claim to fame turns out to be entirely false - but a decent guy in other ways. Badly dressed. Divorced. Putting on weight.
Jerry Cole - 53 yrs old - disabled IT expert and criminal information vendor.
Rich Roberts - 35 yrs old - English hardman actor, who acts tough but who wants to do serious work - the only problem is he can't quite read the words.
Alex - 52 yrs old - white, loosie goosie hippy rich guy who has lost his money and is getting desperate but trying not to.
Scarlet - 45-52 yrs old - unshaven female spiritualist and hippy with a love of exploring the wilderness. Very into journeys.
Chad - 29 yrs old - pretty boy misogynist Beverly Hills party boy. Made money, but not as cool as he thinks he is.
Tae Wong - 39 yrs old - somewhat incompetent Chinese mobster, loves doing ecstasy, going to raves.
Taes Translator - 45 yrs old - VERY STRAIGHT LACED Chinese translator, terrified of his boss's dad. Male, awkward. Needs to speak Chinese."
