The web search results indicate that around 80% of the staff that worked on GTA 4 is still part of Rockstar North and involved in the development of GTA 6. This includes veteran developers like Aaron Garbut, the Art Director who has been with the series since GTA 3, as well as Sam Houser, one of the studio's original founders, and Rob Nelson, the developer who directed the acclaimed Red Dead Redemption 2.
Despite the departures of some notable names like Leslie Benzies, Dan Houser, and Michael Unsworth, the core team behind Rockstar's previous critically acclaimed titles is still largely intact and working on GTA 6. This should provide reassurance to fans that the game is in capable hands and will likely uphold the high standards set by previous entries in the Grand Theft Auto franchise.
80% of Rockstar's Veteran Developers Still Involved In GTA 6
GTA 6 is coming more than a decade after GTA 4, but a former Rockstar developer states that the teams behind both games will be similar.
tech4gamers.com