* Dual Compact Flash memory card slots...this is as good of a time as any to move to the new CFast 2.0 compact flash cards. Whichever memory card format Canon decides to use, I just hope Canon uses the same memory card format for both the new 1DX Mark II and the Canon 5D Mark IV, so those of us who own both cameras don't have to carry different types of memory cards with us all the time.[/b]
That's a terrible idea. Maybe five years ago, but not now. At this point, it would make a lot more sense to just adopt dual SD with full UHS-II support. SD's maximum speed (512 MB/s) is almost as fast as CFast's real-world performance after factoring in SATA overhead, but is a lot more broadly compatible and a lot cheaper.
Also, CFast is probably a dead standard at this point. A few years ago, the SATA folks realized that there was no feasible way to make SATA scale to the speeds of modern SSDs, so they basically stopped developing SATA and started developing a way for devices to use the same pins for a completely different signaling standard (PCIe). The only way CFast will ever get any faster than it is right now is if they do a major redesign of both host and card hardware.
More importantly, one could extend the SD card standard to communicate using PCIe just as easily, but with SD, there are enough extra pins to provide 2x PCIe instead of 1x, so a pin-compatible SD card design based on PCIe would utterly stomp any PCIe-based CFast standard into the ground unless they also change the CFast pinout in what is likely to be an incompatible way.
Given that SD is more than capable of handling the fastest flash cards currently in existence, is cheaper, is more ubiquitous, and is better capable of scaling to faster speeds than CFast in the long run, it's really hard to justify going with CFast, IMO. About the only rational reason to do so involves trying to keep two standards groups competing against one another for petty patent portfolio reasons, and that just doesn't justify the consumer harm, IMO.
Quite recently, my worst fear about SD cards came to fruition... I did a large expo... a combo of raw images and some grab videos... We were the featured photographer... didn't record to both cards, but had 1 cf and 1 sd, filling each up individually subsequently... Anywho, i removed the cards after the expo, plugged them into the computer, the CF card popped right up on the computer, the SD did not... I grabbed another card reader, nothing... i looked at the card and to my dismay, the entire side of the flimsy card somehow broke off! that's why it wasn't reading... crap... nothing was working... luckily I was able to gently reinsert the card back into the 5d3 and it started reading it... so i had to USB import it over... Ironically it still would read in DPP or Canons utility like it normally would, but apple's iphoto saw the files and allowed me to copy the images over... After the card was done copying, i cut up that card and destroyed it... But WTH? I've used CF cards for well over a decade and only had 1 fail on me (a CF microdrive) and another have a corrupt file here and there which made me stop using that card. But never anything like this.