To briefly discuss this topic. I'm sure many people know more in detail info then myself. What basically happened was that Boeing announced that they would hold of the research and development of the 747X and go through with the development of a faster jet. One that will travel at around MACH .95 or faster. They have a drawing of what they believe it will look like on their website. The jet will hold around 250-300 passengers, I believe. From what I read in other discussions the jet may encounter problems at traveling at .95.
I hope this helps a little