According to Game Informer's Loose Talk section in issue 190, Rockstar Games have the next instalment nearing completion for release.
This isn't DLC talk either, they really do mean a whole new game powered by the GTA4 engine. They say to expect a subtitle game much like Vice City/San Andreas was to GTA3.
Of course there is absolutely no concrete evidence to support this rumour, and frankly it seems unlikely what with Rockstar Games working on the DLC episodes for Grand Theft Auto IV.
They wouldn't want their hard work to be overshadowed by such colossal news as GTA: 'Insert City/State Name Here' being released this year. Of course Vice City was released only a year after Grand Theft Auto III was.
"We're not talking about new DLC or a collection of previously available DLC, we're talking about a full retail game. We expect this title to follow the suit of previous GTAs and use a subtitle such as GTA: San Andreas, etc. Tokyo might be a possible setting for the game, but details are non-existent at this time," reports the magazine.
Tokyo has long been thrown around the rumour circuits for a possible setting in a future GTA, with London also a hot contender given the British themed expansion to the original.
Right now it's best to file this under 'fat chance', the very same chance that cop has of collecting his pension slip in the shot below: