A permit filed today with the Orange County Comptroller seem to indicate that work is underway on the new nighttime spectacular at Epcot.
The permit describes the work as:
Installation of four new mooring dolphins, permanent anchors, platforms and bollards.
Location for the work is in the mooring lagoon for the IllumiNations: Reflections of Earth barges. This new infrastructure seems to indicate that there is a need for more docking space, which would be the case if barges and such for a new show was coming soon.
Disney has yet to formally announce the new nighttime spectacular that will replace IllumiNations, but all signs point towards it debuting before 2021.