Well, Gamescom seems all the more certain now that Rockstar are confirmed to be at the EB Expo in Australia, of all places, this October.
Despite it being Australian I've never heard of this event before but seeing as Max Payne's marketing (including the DLC) will be all over by then, I think it's safe to say it'll be all about GTA V.
Edit: Rockstar have actually been removed from that list so I apologise for posting it. I can, however, assure you they were originally on it.
You can see their logo on an ad for the event here: Click!