A freelance sports shooter I know sold his 1DIV and cancelled his order for the 1Dx after using it for LAX and baseball. He had ordered it for his wife as an upgrade from the 60D, tried it out, and couldn't believe how good the IQ and AF were. He promptly ordered a grip for it and another 5 DIII after canceling that order for the 1Div and he's put out stunning work with it.
I would say the 5Diii is the 7D upgrade in every way but FPS, which is pretty much on par with the 50D.
Sony A99ii, RX-100ii, Sonnar T* 135mm f1.8 ZA, Planar T* 50mm F1.4 ZA, 24mm f/2 SSM Distagon T*, Minolta HS 200 2.8 APO, Minolta 2xTC APO, HVL-F43M