First of all, the 747X is not cancelled. I would like to see the press release where Boeing has announced the outright cancellation of the 747X program. Whether we see the 747X fly is questionable, but I hate to see poeple say that the program is cancelled when it is still alive.
It seems to me that fuel comsumption data for the "sonic cruiser" is very near that of current aircraft because airlines wouldn't want it if it were a "gas hog". But I have read that interest for the "sonic cruiser" is very high. Some analysts have said, "if Boeing can make this aircraft work, you can write off Airbus right now". A bit of an exageration. However, I do believe that Airbus was a bit blindsided by this new aircraft announcement.
I'm not a real aeronautical engineer, I just play one on Airliners.net.