This information comes courtesy of Total Film, which has a full spread about Captain America: Civil War in the new issue. In an annotated piece of concept art featuring members of Team Iron Man doing battle with Team Captain America, it's noted that Rhodey has a new name as part of the Avengers lineup. The blurb doesn't really reveal anything new about the character's role in the film, but you can read it below:
Old Shellhead's greatest ally, War Hammer (Don Cheadle) looks to get into a spot of bother in Civil War – the film's trailer shows his pulverised body being cradled by a distraught Tony. Could this be the end of the line?
There is no War Hammer featured in Marvel Comics (unless you count Mjolinr), and it's a bit strange that they would go with that name given the existence of the geeky tabletop wargame Warhammer 40,000. That being said, the name is a bit more PR friendly, so it's understandable why he would change it after joining the Avengers.
It's entirely possible – if not likely – that the new name is mostly meaningless, but the choice does generate some speculation in my mind. Specifically, the War Machine armor was initially upgraded by Tony Stark's rival, Justin Hammer of HammerIndustries. We haven't seen that character, as played by Sam Rockwell, since theIron Man 3-themed One Shot All Hail The King, but perhaps he could somehow reemerge in Captain America: Civil War?
We don't really know what to expect from Don Cheadle's part in Captain America: Civil War, though he could actually play a significant role given his relationship with the aforementioned Tony Stark (the movie's prime antagonist). It may be a while before we getting any new info, given that the first trailer just dropped a few weeks ago, but we're excited to find out more.
Captain America: Civil War is directed by Joe and Anthony Russo, and is based on a screenplay by Christopher Markus and Stephen McFeely (the same four men who brought us Captain America: The Winter Soldier). Look for the film in theaters on May 6, 2016, and stay tuned for more updates.