MTH has just announced (on 5/9/18) a new production run of Big Boys that includes additional new road numbers (4014-Coal, 4006, 4017, 4018, 4023 --- All of these are Coal engines) (Catalog also includes 4014-oil from prior catalog)
MTH new release: https://mthtrains.com/news/613
Download PDF: MTH-OneGauge-Catalog-2018(BigBoy).pdf
Per this announcement new engines will start arriving this July 2018. Depending on quantities that arrive it could be delivere