Recent rumours suggest the opposite, that the team behind GTA 5 are busy at work putting together new game projects, which include GTA 6.
Source: GTA 6 release update as PS5 news offers exciting Grand Theft Auto prospect

Recent rumours suggest the opposite, that the team behind GTA 5 are busy at work putting together new game projects, which include GTA 6.
Source: GTA 6 release update as PS5 news offers exciting Grand Theft Auto prospect