Internal calendars have indicated that the Walt Disney World Railroad will be closed through at least October 2020, according to Mike at Blog Mickey.
In case you didn’t know, the Walt Disney World Railroad system has been closed since the 18th December, 2019 as TRON Lightcycle Run construction takes place across the tracks in Tomorrowland.
As part of the new roller coaster construction in Tomorrowland, the railroad tracks have been removed. Eventually, the train will return, and will pass through a tunnel as see in the concept art below:
At this time, there is no announced reopening date for the Walt Disney World Railroad.