As Tony and Rhodey are fighting, Stark mentions he has back up coming to him. This builds up the anticipation factor, because who else can Tony really call on for back-up besides Rhodey. Then the suits fly in and surround the area.
The staging for the last scene was the best open space to "Start from scratch", as Tony commands Jarvis to destroy the suits. With the scene being set up so perfectly, this created the best use for the set. The open and wide skies were great to direct the audience's attention to the space to witness the destruction of the previous suits.