"Annoying" is an understatement. Although I wouldn't abandon Canon for Nikon, I would definitely not be happy. However, I think we are putting the cart before the horse here.
I am very confident Canon executives and marketing strategists are wise enough to realize that a new high-end body (or any body, for that matter) must work with the existing EOS lens line. It would definitely be corporate suicide to alienate the entire market audience for your "flagship" camera line.
Although I do think the EOS lens line will be "fully retired" someday, I think that day is a long ways out.
If the Canon executives are smart, they would simply create a body with a few extra contact points (or a slight re-wiring of the existing patterns) that would be used by the (rumored) EF-x lenses and "ignored" by the EF lenses or EF-S lenses. This approach would give consumers the ability to slowly integrate the new lens line into our existing EOS arsenal (as our current lenses get damaged, etc).