Here's how I see it:
There's three universes currently.
Each with their own style.
Now, when it comes to characters:
- If a character appears in another Universe in their old universe state (Madd Dogg, Donald Love, OG Loc, CJ on Fruntalot), it's an Easter Egg
- If a character appears in another universe but now looks different and acts different to how they were (and have altered stories) that's simply THAT universes version of the character
What does that mean, well Rockstar CAN bring anyone back, but as stated, they would be altered, changed somehow to fit this universe, Lazlow had some changes, Fernando had a couple of huge changes, Willie looks nothing like he did in VC and has a different VA, etc.
Same way El Burro existed in both 2D and 3D era, he appeared in person in the 2D era, but in the 3D era he was only a phone contact, voiced by a different person, but still implied that he's the gang leader of The Diablos (also, he was changed here as El Burro was in the CITY of San Andreas in the 2D era).
What people shouldn't expect, which is a big thing that those of us who can follow this get annoyed at, characters won't cross over EXACT, people want CJ, people want Tommy, but for theme to appear they would have to be altered and changed to be re-visioned in the new universe. Rockstar implied that in the HD era, Grove Street was lost because that set gave it up and let the Ballas take over, so there's a 50/50 chance here that CJ is either dead here, or he's now some pussy living away from the gang life that he couldn't defend in the past.
PS: Some people seem to think I'm getting angry about this or something? Is it because I do some words in capitals? I realise that may come across as me randomly shouting but I do that to just make a point on that word or sentence following, I'm really not screaming at the computer, haha.
PPS: And I keep bringing up Batman as that's like the perfect mainstream example of this being done, Batman has like 50 different universes, maybe more at this point which play into all tropes that GTA has barely even touched on. An example someone brought up earlier about Voice Actors, again, Kevin Conroy and Mark Hamil voice Bruce Wayne/Batman and The Joker in TWO Universes, the Animated Series Universe and the Arkham Universe. To go one step further, both of those universe have the same Lead Writer, Paul Dini.
PPPS: I guess being a bit of a comic book geek helps my side a bit, like seriously guys, the GTA Universes is nothing compared to the spider web that is the universe of Batman, Marvel and Doctor Who.