Grand Theft Auto 5 was released back in 2013 and players have been waiting on news of the franchise's future more or less since.
But nearly six years later, by which time many franchises would have rolled out as many new entries, we don't even have official confirmation that there will be a GTA 6.
Obviously we know there will be a GTA 6 due to hypothetical references to the future of the franchise and the obvious profit that GTA 5 has been generating all this time, but players have been waiting for more than half a decade now. That said, this isn't unusual given the franchise's history.
It may all be about to change though...

Rockstar is known for being secretive and taking its time between releases. Seven years passed between the two Red Dead Redemption games and five years passed between GTA 4 and 5. Speaking with Gamesindustry.biz, Take-Two Interactive CEO Strauss Zelnick touched upon this topic, and stated that if anything, the time between future releases will be decreasing instead of expanding even further.
I don't see it expanding further. In fact, I would expect in many instances it may compress.
The success of the GTA Online model may have been part of what influenced Rockstar and Take-Two to sit on any future game in the GTA franchise, since the constant engagement with the player base through DLC and microtransactions — as controversial as they may be — has proven to be a great source of income. Due to GTA Online's continuing success, it seems like Take-Two felt no great rush to get to the next game.
However, the way the industry is shifting, Take-Two may have more of an inclination to release GTA games more frequently going forward. Zelnick mentioned that Rockstar's development teams have grown and the tools used in the creation of games have improved, which could factor into shorter development cycles.
On the other hand, the increasing prevalence of the "game as a service" model seems attractive to Take-Two, and they might prefer to release shorter, smaller games more frequently, which they then intend to support with further content.