USG is making serious plans towards increasing production (again) at their Plaster City plant. Related to that will be the need to increase capacity to deliver rock to the plant. Expanding the capacity of the narrow gauge is being considered, but also other options including standard gauging or other transport methods.
The single biggest drawback to the narrow gauge's expansion is availability of appropriate locomotives (They want a 3rd to allow 2 on the train and 1 in the shop). Some sort of decision may be made (at least as to the mill expansion) as early as next year.