I've no interest in the video functions Canon thinks important. Cropped-sensor 8-bit 4k? Might as well go Sony. Uncompressed full sensor please.

My interest in this camera will depend completely on sensor read time (i.e. how bad is the rolling shutter in full-frame video), whether Magic Lantern can be ported to it, the size of the buffer, and the combined write speeds of the card slots. The CF slot isn't CFast, but the SD slot could be very quick.

The biggest limiting factor for recording Magic Lantern raw video on the 5DmkIII is the card writing speed -- you can get to 1080p25 but beyond that you can only record til you fill the buffer (people have managed a few seconds of great-looking 3.2k raw video: http://www.magiclantern.fm/forum/index.php?topic=16439.0 )

So if Magic Lantern raw video becomes possible on the new camera, and it's possible to write at the speeds necessary for 3k 23.98fps or better, that'd be a significant improvement over the mkIII. If the card slots are no faster than those of the mkIII, then even if Magic Lantern is ported we'd likely be stuck with the same limits.

Another free subtitling application is 'Jubler'. Worth a look:
http://jubler.org/features.html