Yes, Coach 256 is part of the planned consist. The consist which will hopefully be ready next year will be backdated RPO 64, Coach 292 and Coach 256. Future additions might include immigrant sleeper 470 (under restoration by the Friends in Colorado Springs), a baggage car, and a business/pay car.
These cars are going to be impressive restorations, just like 168 itself. Coach 292 has pretty much been completed (except for installation of the passenger trucks) and looks magnificent inside and out! Photos have been previously posted here. This train will be something to look forward to!