It's been reported on Kotaku that an accidental leak by Shawn Fonteno, the voice behind GTA V protagonist Franklin, has revealed that GTA: San Andreas' central character, Carl “C.J.” Johnson may be returning to the series, possibly in future DLC.
At a panel at Comic Con 2013, Fonteno was asked which past GTA Protagonist he would have liked to have voiced, and he responded with San Andreas' hero, C.J. However, he then said he wasn't so disappointed he missed the chance, as he's working with C.J.'s voice actor, Young Malay on another project. He was asked to elaborate on this, but promptly changed the subject, hinting that he wasn't actually supposed to reveal that juicy bit of information.
Of course, just because Fonteno and Malay are working together on a project doesn't mean that it has to be GTA-related, but you have to admit, it sounds like much more than a mere coincidence, and the fact that GTA V has plenty of homages to Grove Street and GTA: San Andreas in general, it's likely that DLC will touch upon the game's successor in more detail somehow.
As Kotaku has also noted, if C.J. was to return, he'd be in his 40s, as the original game took place in the early 90s, whilst GTA V is set in 2013. Any story involving him would also be interesting as the Grove St Families have clearly fallen on hard times, as Grove Street itself is now run by rival gang the Ballas (take a trip to Grove Street in GTA V and you'll see plenty of purple outfits). Could there be a 'take back Grove St' DLC incoming?
We'll have to wait and see if any DLC will dig up Los Santos' past, so stay tuned for more news as we get it.