Rockstar's launch messaging for GTA 6 is all about the story of Jason and Lucia. There is no announced online mode at launch, and no official window for one.
What about the rumors?
Some sites claim GTA 6 Online is coming in early 2027, and a few list specific modes and player counts. None of that comes from Rockstar or Take-Two, so treat it as speculation.
What this means for roleplay
Community roleplay servers (like FiveM for GTA 5) run on PC, and GTA 6 has no PC version announced yet. Until then, the GTA 5 roleplay scene is still massive: find a city on GTA Server Hub.