I predict that the numbers 787 and 797 will soon be attributed...
The 737 is getting long in the tooth, and Boeing has I believe already announced that the -900 variant will be the last one. It has served well, but I think airlines and passengers will want something new soon. My prediction is that the successor to the 737 will be the 797, and that Boeing will announce its development sometime in 2001.
The 747X project maybe kinda stalled right now because airlines (and passengers) are starting to realize that the 747, as wonderful and capable an aircraft it has been, is over 30 years old. Orders and deliveries of this plane are slowing down substantially (only 21 orders in 2000, many of them cargo).
The 747X will be a good opportunity to make MAJOR changes, not just stretching the fuselage. It will certainly have a new wing, will probably have FBW like the 777, different engines, 777-style interior. They can also do some major changes on the structure, using composite materials (a process already started somewhat with the 747-400). If they really want to be smart, they will make the cockpits common between the 777, 747X, and why not even the 797 (737 successor). The only difference will be extra controls for 2 more engines. Airbus did it, and cockpit commonality has proven to be a big asset for them.
With so many changes, why not mark the occasion by retiring the honored 747 designation gracefully, and naming it the 787. It would also be a signal that this is not just a lengthened 747, but a practically new plane (after all the 727, 737, A330 and other "new models" took a lot of parts from previous models). The fact that it will look a lot like a 747 does not mean it IS one. Otherwise the 747 would have been called the Carvair II
That's my crystal ball.
The only thing you should feel when shooting a terrorist: Recoil.