The Marvel Studios project that seems to be farthest along at this point is the standalone Black Widow movie.
There has yet to be a confirmation from Marvel Studios in regard to the Phase 4 project that will begin production next summer.
Phase 4 of the Marvel Cinematic Universe is starting to take shape and it looks like Marvel Studios is looking to move forward in June of 2019, according to a new report.
There are also hints that the MCU Phase 4 project to begin filming next summer is The Eternals, which is currently being written by Matthew and Ryan Firpo.