DX12 is really a non issue for a while.
You need windows 10 and a game that supports DX12(only a few do)
The benefit is a faster multithreaded path through the graphics driver. But the driver is not the major part of the cpu need for a game.
So, yes, DX12 can help a bit if you have a many threaded processor with weak cores like the FX.
But, performance will be better with a processor with stronger single thread performance.
Long term, DX12 will let you combine disparate graphics cards. It remains to be seen how well that would work out.