To go along with that rumor, the one about the release date for the PS5 is pointing to a release before 2020. If the game is ready before that it would make sense, but it would have to developed for any other technology that could come with a console that has yet to arrive.
Grand Theft Auto 5 brought a whole new world to the game series and required the power behind the PS4 and the Xbox One in order to be played properly. The same would be said for GTA 6 as it is entirely possible it will be even more involved that previous titles.
Only time will tell and in the meantime, fans are going to be waiting around to see if they will be able to get a handle on any news that Rockstar, Microsoft or Sony might even consider throwing its way. One rumored feature that will create plenty of buzz is a possible “teleportation” feature coming with GTA 6.