With memory cards supporting UHS Speed Class 3 (= minimum 30MB/s) selling for under U.S.$100, and the smaller form factor, I don't see any reason to keep supporting CF any more.
Considering that my old 7D hit write speeds of >45 MB/s, I don't see a card which would take 50% longer to clear the buffer as a viable option. Also, highest SD card speeds are only achieved after a low-level format, so if you don't perform that time-consuming in-camera task frequently, your speeds get even slower.
Time consuming? Takes no more time at all to initiate the function, and the actual format only takes a few seconds, of which you are not obligated to watch it carry out. Hardly a valid argument. The write speed issue is clearly a problem. Until the write speeds are improved the buffer fills much to quickly when shooting to SD.