The Canon EOS 1D X Mark III has already been development announced, but according to Canon Rumors, Canon is keeping two major features under wraps until the official release announcement: no-crop 4K with dual-pixel AF, and the ability to record 6K RAW video over HDMI.
CR cites “multiple sources” who claim Canon is holding back two “major” features for the full announcement and release of the Canon 1D X Mark III.
The first is no-crop 4K (ostensibly at 60p) with Dual Pixel AF. The second is the possibility, still unconfirmed, that the camera could shoot 5.9K RAW video to an external recorder over HDMI. That last, most impressive has allegedly not been nailed down yet, likely because of the sheer heat that 6K RAW recording would cause; even in a camera as large as the 1D X Mark III, keeping the sensor from overheating while shooting 6K RAW would be a significant challenge without some sort of active cooling.
Notably, the rumor site also claims that IBIS is still potentially on the table, despite no mention of stabilization in the original press release. From every reliable report we’ve seen, the Nikon D6 will be including IBIS, so it would be a pretty major selling point for Canon if the 1D X Mark III used it to. That said, we wouldn’t keep our fingers crossed on this particular feature.