Gang wars is something they're not going to add for sure, The Families have no actual reason to break the truce with the Ballas.
I'd say that Vigilante might make a return.
You obviously did not follow the story properly. The Families truce with the Ballas was broken halfway through the game, after the failed drug mission with Franklin, Lamar and Trevor. After that incident, the Families and the Ballas were supposed now be at war with each other (although we never really felt it on the streets, but that's another issue).
If there are gangs in the game (which there obviously is), then there are countless good reasons to add gang wars.
Yeah.. but they'd also have to add another protag who likes being a gangster because that one black guy who was a protagonist was kind of smart and gave up that dead-end ghetto life for a life of professional heists and luxury.
Just like the last guy, you too failed to follow the story properly.
Yes, Franklin wanted to do crimes that netted him big money fast, and to live that life of luxury. But giving up the ghetto life is not necessarily the same as giving up being a gangsta. Franklin is still a gang member, he never once mentioned anything about leaving the Families. He just did not want to continue to engage in low-level street hustling and crime anymore, because it was not financially rewarding enough - and he wanted to live a better existence in luxury away from the ghetto. That is all it was.
He still wears gang colors in his green clothing, he yells out his gang's name when shooting at gang rivals, he still agrees to put in work with his gang, and he still hangs out with his fellow gang member Lamar. There is every reason for Rockstar to add a gang-centered DLC to this game. Rockstar's own words, "Franklin is a gangbanger in a post-gangbangin' world".
So no, you're completely wrong bro.