This game is poorly optimized and even with DX11/12 it wouldn’t support multithreading, DX11 and above does support multithreading, but core game doesn’t, so it wouldn’t have any effect about that, it would improve performance a bit, but not by much. It would be nice, but I doubt it will ever happen, they would most likely have to build around a whole new engine and that won't happen anytime soon, if at all.