True or not, you really have to ask yourself how much longer you can hold out with that extremely old processor, especially when games are more and more being designed around multi-core and take more and more advantage of them.
Yeah, it is getting to the point where it's common for me to worry about whether it will play certain games adequately, but usually the ones that are too laggy to play at all aren't worth playing and horribly optimized. I spend just as much time, in fact more so, speculating about poor game development as I do my rig's capabilities. It's really hard to justify short, expensive upgrade cycles on PC hardware when we get such crap ports all the time.
It's rather ironic too that despite Crysis and Warhead still being used by many as THE benchmark references due to their hardware choking nature, they are two of the titles that play quite well on my rig, but that's partly due to my using common sense in choosing settings carefully, along with a few Cvar tweaks.
Many still don't even know for instance that Crytek caps the usable video memory to 256MB. Unless you use the proper Cvar tweak, any GPU larger in memory, of which there are many now, will only use 256MB. I'm willing to bet even some trusted game review sites that spew lots of tech info about hardware, drivers and settings don't even know that or use that command.
That being said, I have planned a new build for some time. Originally it was slated for end of '07 with E6700, 8800GTX, and 2GB RAM. Then end of '08 with i7, GTX280, and 4GB RAM. Now I'm looking at probably X58, i7, GTX300, 6GB RAM, and e-IPS display(if a larger one is made).
Last build (this one) I didn't time very well, paying a lot for the X800XT that had just come out, suffering through about 4.5 yrs now of X800/X1000 series stutters/bad drivers, and puttting up with a rather clumsy dual CRT disaply setup. This time I want to make sure I'm happy with what I pick out for some time.