https://www.overclock3d.net/news/software/gta_6_appears_in_the_resume_of_former_rockstar_artist/1 GTA VI is in development, at least according to the 3D artist Bibin Michael, who has listed experience creating concept vehicles for the upcoming game on his website resume.
While Rockstar has not officially announced Grand Theft Auto VI, it is probable that the game will be created for next-generation console platforms, perhaps acting as a next-gen exclusive. That said, Grand Theft Auto V was a multi-generation release, spanning across PlayStation 3/Xbox 360 and later PC, PlayStation 4 and Xbox One. If Michael's resume is anything to go by, Grand Theft Auto VI has been in development since before Red Dead Redemption II release. Rumour has it that Red Dead Redemption II will be announced for PC within the next few weeks, potentially bringing the game's visuals to the next level through the power of modern PC hardware.