Will the King Coal/Tolsia Highway be completed as proposed? It seems to be taking forever to construct, just like the Coalfields Expressway (US 121).
Probably not. There's not really that much traffic and the population continues to decline in that area. There isn't the demand for it and WVDOH has more pressing needs for their very limited funding stream.
There are programmed projects in the STIP to extend construction from its current end up to WV 123. That section makes some sense as it will function as a bypass of Bluefield, where traffic has to drive on city streets and through downtown for 4 miles. Nothing else is programmed from there into McDowell County and I don't expect anything further will be constructed.
Over along the Mingo/Logan line, there is a section under construction immediately east of WV 44. That part is going to be completed to Gilbert Creek Road. That section is useful as it bypasses the eastern approach to Horsepen Mountain which is the worst remaining section on US 52 in West Virginia.
WVDOH has been doing planning and permitting to extend the current King Coal section around Delbarton. This is tied to a mountaintop removal coal mine. If the mine happens, it'll probably get built. If it doesn't, it won't.
On the Tolsia Highway section, there's a decent chance the 4-laning will eventually extend from its current end at WV 75 down to Prichard especially if traffic picks up at the intermodal terminal there. I could possibly see it being extended to Fort Gay. Beyond that, I don't see WVDOH doing anything. Most of the road is reasonably high speed 2-lane already and traffic counts are fairly low.