The replacement is the Canon 1D X. It's slightly lower resolution at 18 megapixels instead of 21 and image quality is fairly similar at iSO 100. However, in almost every other respect it's a much superior camera, faster, more responsive, amazing high ISO, more full featured. If you're a studio shooter no need to worry about upgrading, however if you shoot action/events/location/etc, it's well worth a look. I upgraded from the 1Ds III to the 1D X and am very glad I made the switch (although it's an expensive upgrade).