Is that the name of the next GTA or guesswork?
Guesswork. But if they call the next installment GTA VI, then marketing wise it makes sense
This was a mock-up on reddit
They tend to like using the same locations over and over again (which I'm fine with, you get a history of the place, etc).
London - GTA London
Liberty City - GTA, GTA III, GTA Liberty City Stories, GTA IV,
Los Santos - GTA San Andreas, GTA V
Rest of San Andreas - GTA, GTA San Andreas
Vice City - GTA, GTA Vice City.
Not to mention everyone likes to debate which was best, San Andreas or Vice City. Vice City easily had the better environment.
So yeah I'm guessing... but I think it's a good guess.