For more information about the Infinity War Blu-ray where you can see the Avengers 4 set interviews, you can head over to Marvel for more details.
The Russo Brothers are currently in the editing process, after taking some time off to promote the Infinity War Blu-ray.
Filming for Avengers 4 started in August 2017 and lasted all the way until January 2018 during the post-production process of Avengers: Infinity War, which was just recently released on Blu-ray.
The two were newly engaged at the beginning of Infinity War, right before Stark took off to save Doctor Strange with Peter Parker.