An update from the developers at Hangar 13 paint a bit of a sad picture for the PC release of Mafia III on the eve of its launch. The team says that the game is currently locked to 30FPS due to parity with the console versions. Ah parity, we meet again.

So yes, while the game will launch with a 30FPS lock, it sounds like the team is working on an update that will allow for higher framerates. Why this was not included prior to release is really anybody's guess.