Mafia III was supposed to be in development. And with the closing of 2k Czech, the project is rumored to have been shifted to the U.S
Take Two is the parent company. And both Rockstar and 2k Czech were reported to have worked closely together on GTA V. Who knows......maybe the soon-to-be-announced title may not be an original R* title at all.
But the chances are slim. R* may not jump from one open-world game to another in rapid succession. Bully, Agent, Manhunt are all strong possibilities.