War Machine without the Gatling gun? I call bullshit on that one!
If you scroll down on this page, you'll see a photo where the gun is visibile on his back (at least I think that's the one you mean):
Also no way that armor will be used by a villain. It just looks too damn SILLY. It should be obvious Tony will make a joke about it the moment he sees that thing.
I don't see it being around for more than a scene or two though. It'll be very easy to repaint it back to the gray and black armor that we all know and love.