But some new insight could give us an indication that it has been a lot longer than that.
Let's look at the new evidence and see why that may be different.
GTA 6 In Development Since 2014?
In a now-deleted Reddit post, Chris Liberty revealed via a livestream that the next GTA game has been in pre-production since 2014.
This is interesting for a few reasons, the first of which is that it would seem contradictory to the statement that the next game is in "early development". To have a 6-year pre-production seems far too long to only just start development itself.
Rockstar Games traditionally focus on just ONE title at a time, meaning that they were working on both Red Dead Redemption 2 and GTA 6 at the same time.
This could have been what influenced part of the "crunch" employees saw with the release of RDR2.
It could also mean that we're so far from GTA 6 due to the overwhelming amount of development that RDR2 required.
It wouldn't be a surprise to see Rockstar Games learn from the error of their past. With GTA 5 the developers opted to launch the game on the older generation before the new one came in; then delaying the publishing on the next generation for a year; not to mention that GTA Online didn't come until a month after it's initial launch.
Perhaps Rockstar Games have tactically played this to wait for the new consoles and focus their efforts on creating a game that can utilise the new technology AND avoids a split fanbase.