All they can do is make it look, feel, and interact like real life and that's really all the further they can go. I think after a couple years of DX10 and it will be about as realistic as it gets. But, it's not all in the graphics, it's how the environment reacts to your actions and how the physics of the games are.
the only thing is that the clouds have no shadows.... which is something that i've always hated about directX and pretty much everything else... light and clouds have no connection when you make the program