Well, the trend is, of course, the latest technology comes out (DDR?) and all the stuff just below it gets a lot cheaper. The guru's and the few people that actually need the new performance level buy the new stuff; the mainstream then upgrades to the now "just" obsolete stuff for a very attractive price, and so on. My point is that this isn't happening because the latest technology doesn't really exist, ie no functioning 760's, no C T-birds, etc. Therefore, no major price break on the level just below these. Your point is that the "obsolete" stuff is still quite functional for mainstream users. True enough, but it raises an interesting point.
If the next generation of software of whatever genre is coded to maximize the performance of the P4 (Intel is probably powerful enough to make this happen), then everything other than P4 trying to run that software will truly be obsolete. Then everyone must upgrade to run the new generation of software. Intel saves the world (again?).
Paul