Recently a lot of GTA 5 players received a popup ad in the game that showed 2019 release year for GTA 6 / GTA VI. There was no prior announcement regarding GTA 6 / GTA VI from Rockstar Games before this happened.
It seemed fake at first for a lot of users considering 2019 as the release year for GTA 6 while many users also believed it to be true. But finally the news was confirmed fake by Rockstar Support in the following tweet :-
This is a hoax made with the use of mods, and not an official message or statement from Rockstar Games. *OV
— Rockstar Support (@RockstarSupport) July 2, 2018
Redditors also believed the fake announcement could have been through the use of mods as it only occured to PS3, XBOX 360 and PC users. Those are the only versions of GTA 5 that can make use of mods in single player mode. Rockstar Games is currently focussing on Red Dead Redemption 2 and apparently GTA 6 / GTA VI isn’t coming anytime soon, reason being the insane popularity of GTA Online.