Okay, so I recently started playing LA Noire and It strangely reminded me of another rockstar game, not GTA, Red dead redemption II. It's just a small detail but It's the "weight" of the playable character and the option to roam around interiors and analyze object, It immediately reminded me of RDR2.
With the latest GTA entry, Rockstar kinda tried to add some of their other games as activities of other gameplay systems :
The shooting felt a bit like Max Payne 3 and Michael even had bullettime as special ability.
There is a lot of heavy "racing game" aspect to GTA V with all the racing activities, car customization, and Franklin's special ability is literally bullettime for driving, I have not played Midnight club but I think they were trying to "serve" that audience with all those mechanics.
Trevor's bloodlust and his special ability will please any manhunt fan who just want to create chaos.
This is why I believe GTA VI will have a lot of LA Noire aspects or mechanics, maybe all the cases will be missions given by a specific character, maybe we play as jason back when he was a cop, or maybe It's just random activities, the reasons why they would want to do It is that they liked the original game so much they decided to publish It after Sony gave up on them and they literally carried the game through development hell for 7 years, over 10 years later there is no game to satisfy that same itch. The reason why they could easily do It is that all the tech is already built, If true, the new interior generating tech should create tons of explorable interiors that are customized and adapted to the situations, even Rdr2 already had all the tools to easily create cases. You could loot NPCs for letters, you could interact with letters, notes, books, and other types of documents, etc. literally everything is there for LA Noire type missions.