What I want to see is characters that can equip physics-enabled equipment, like robes and cloaks that bend and blow in the wind, or shackles with chains dangling from them (we do start out in prison, after all). And of course, we NEED better hair physics. Back in oblivion, hair couldn't even be weighted to the skeleton, so long hairstyles were doomed to stick out like they were made of metal...
(Do note, I haven't actually played fallout 3, so I don't know how the physics engine improved between Oblivion and then lol...)
What do you think we'll be seeing?