According to latest news, Rockstar North nodded to the possibility of "Grand Theft Auto" in London. This speculation made more sense after statement by Dan Houser, Rockstar Games Co-founder, that for now the game plans to market with their existing, American-type brand image. This means that "Grand Theft Auto," including "GTA 6," will feature only in English-speaking setting. If Rockstar listened to the fan's request for "GTA" outside US, then up next will be "GTA 6" set in London.
If that is indeed the case, this news will lend credence to the fact that "Grand Theft Auto 6" might include world events and that London will make an effective set-up for the reported "Bonus International Mission."
However, with latest UK Brexit event, the marketability of "GTA 6" with a London map may not seem so plausible anymore, even though UK is expected to iron out the wrinkles in its three-year Brexit implementation phase.
But it is important to note that Brexit timetable may not give "GTA 6" production team to change with the changing market. If Rockstar were to take its cue, perhaps this would be the time to ditch London map and double the size of US map as its "GTA 6" offering to the fans.
But Dan Houser promises that "GTA" will eventually reach other non-English speaking countries. Rockstar has already attempted this by sending its R&D team for location scouting in Tokyo, Japan.
While Brexit certainly puts the fate of London map in question, "GTA Online" micro-transactions are successful enough to allow Rockstar to take its time with GTA based decisions, in or outside of London.