Tony Stark is indeed bankrolling The Avengers this time out. With the dissolution of S.H.I.E.L.D. in CAPTAIN AMERICA: THE WINTER SOLDIER and it's subsequent "handover" to Phil Coulson in Agents of S.H.I.E.L.D., Tony Stark takes on the role of global security by housing The Avengers in the former Stark Tower, now Avengers Tower (featuring the "A" on the building, as teased in both Cap 2 and the end of THE AVENGERS), where he funds new tech, new costumes, and even a new Quinjet.
Stark wears the Mark 43, a suit with less gold on it than IRON MAN 3, but still more than in THE AVENGERS. The chest core reactor will be back to the circular shape favored by director Joss Whedon. The Mark 44 is the Hulkbuster and will be his other suit in the film.
War Machine is confirmed for a cameo, but won't feature throughout the main storyline