GTA Online Will Continue After GTA 6 Launches
Take-Two has confirmed that GTA Online support will continue beyond GTA 6's November launch, but it has not announced a GTA 6 online mode.
GTA Online will keep receiving support after Grand Theft Auto 6 launches on November 19. Take-Two confirmed the plan during its September 17 shareholder meeting, describing the existing online game as a robust business that it intends to continue supporting.
That is useful confirmation for players who have spent years building characters, businesses and collections in GTA Online. It is not an announcement of a GTA 6 online mode, and Take-Two did not provide a shutdown date, migration plan or replacement schedule.
The current GTA Online is staying active

Rockstar is still updating GTA Online. The recent Kortz Center Heist update added a heist, vehicles and Mission Creator changes alongside stability fixes. Continued support therefore means more than leaving the servers switched on, although Take-Two has not promised a specific update cadence after November.
This does not confirm GTA 6 Online
The shareholder comments concerned GTA Online as it exists today. Claims that a new online game will launch with GTA 6, arrive with a PC version or replace the current service remain speculation until Rockstar announces them.
What players should do
Keep playing the current game if its progression still matters to you, but do not spend money based on assumptions about transfers into a future service. No character, currency, property or purchase migration has been announced.
The confirmed position is narrow: GTA Online is not being switched off when GTA 6 arrives. Everything about its eventual successor remains open.