No, cross-platform play is not confirmed for Grand Theft Auto 6. The game launches as a single-player title on November 19, 2026, for PlayStation 5 and Xbox Series X|S. Rockstar has not announced any online mode, let alone cross-platform support for it. Anything claiming GTA Online 2 or crossplay is speculation.
What is confirmed: both console versions exist, but there is no word on cross-save, cross-progression, or cross-generation matchmaking. Since the game ships without a multiplayer component, the question of crossplay simply does not apply at launch. Rockstar bought Cfx.re in 2023, the team behind FiveM and RedM, but no mod or server tools for GTA 6 have been announced.
If an online mode arrives later, cross-platform support would be a separate announcement. Rockstar has not made one. Until they do, plan on playing solo on your own console. PC players have nothing official to expect either, as no PC version is dated.