A 14-24 f/2.8 would be a very cool lens, negatives include the inevitable stratospheric price and the inevitable bulbous, vulnerable front element that couldn't take filters. For my priorities, use and needs, such a lens would come a fairly close second to an upgraded 16-35 f/2.8 MkIII. Currently my very occasional ultra-wide needs are handled by a very good copy of the Sigma 12-24. These are OK lenses for occasional careful use, but YMMV.
The current 16-35 f/2.8II is a usefully competent lens, but not one that anybody could describe as consistently stellar. Used carefully, it does the job pretty well. The new 24-70 f/2.8II has given us a taste of what Canon is capable of, but given the usual life spans of Canon glass, I doubt there will be a 16-35 f/2.8III for quite some time.