RacerX,
I'm thoroughly enjoying this debate. I thought such cerebral back-and-forths were limited to the roadie forum. After all, what do they have to discuss besides Campy vs. Shimano. . . again. I do like teasing the roadies now and then. They can be so serious.
I do realize that the pros do incorporate updated technology, and the new XTR discs may finally kill V-brakes in the XC peloton once and for all. And the new Spec. Epic looks fabulous, and also may push pros permanently to FS. I confess that I covet one, but, alas, the checkbook won't support such things, and my precious NRS would be very jelous.
As to incorporating a DH section in and XC course, yes, I think it's feasible. Your point regarding body armor is well taken, but I would not advocate a 4 ft. drop or including an "extreme" section of the DH course. If a rider considered wearing body armor or a full-face helmet the spirit of XC would have been compromised. I would hate to see that.
While I hope that XC remains the domain of great athletes - go Cadel - and I'm sure it will, equipment will always play a greater part than on the road. Road bikes seem rather generic to me. (I hope no roadies are reading this thread) Lance could have just as well won 4 Tdfs on any other bicycle. Yes, a Litespeed is different from a Colnago, but you can get both with Ksyrium wheels and Campy Record components, and you'll go just as fast on one as the other. With an XC bike you (the pros) have to decide between FS or hardtail, disc or Vs, tubes or none, knobbies or semi-slicks, etc., etc. With riders making equipment choices for each race, a bad choice can cost them positions. A roadie's biggest decision is whether to wear arm warmers or not, because he knows his bike is going to be set up virtually identically to the other teams' bikes. Roland Green makes his hardtail/FS decision every race.
Finally (for this post, anyway) road bikes have been evolving for much longer than mountainbikes, which explains why road (racing) bikes are so similar in performance, and thanks to the UCI, appearance and weight. XC is still evolving, and probably will for quite a while. Even so, some developments are becoming the accepted norm - 4-bar suspension, for example. It's light, it inherently fights bob and the Epic is taking it to a higher level. Ten, 20 or 30 years from now we might be shocked at how similar all MTBs are. But they will be much better bikes than we have now.