Well I think the point is, if someone doesn't wait until the new processors come out in 09, they might be kicking themselves. Of course, if you HAVE to get a new computer by then, just do it, but if you can wait a bit longer (if the upgrade is more of a want than a need), why not just wait the year and get the computer that has significant upgrades over the one that has minor upgrades? These processors, Merom, Penryn, Montavena are all pretty much in the same generation and more or less offer the same boosts over one another. I think Nahalem is supposed to offer a more dramatic boost based on the way its built.
I guess it depends on what you own a computer for. If what you're concerned about is how much processor intensive work you can get done in a given amount of time, then your best strategy is to buy on a regular schedule. You might tweak a month this way or that to capture the a minor bump, but waiting 6 months for a new machine doesn't make sense-- you're likely wasting time using obsolete hardware hoping to gain an extra 5-10% in performance rather than getting the 30% performance boost you'd get updating now.
If you have a specific need, then there is likely a threshold at which buying makes sense-- for example you may decide it doesn't make sense to buy a new laptop until you can load 16GB of RAM in it because your application is memory constrained. Or you may skip an update because your primary use is gaming and the latest generation hasn't improved the video hardware.
As I said earlier-- waiting for an breakpoint in the CPU performance curve is futile. Intel doesn't do that. They don't release parts that are 30% faster. They sequence changes in microarchitecture, fab process, and chipsets to throttle performance gains over time-- if they linked those releases it would, first, put their engineering, manufacturing, and test resources though massive feast and famine cycles, and second their sales would be a Wall Street galling roller coaster.
The software dev cycle further blurs the benefits of each CPU generation. By the time the next generation of CPU comes out, software *might* just be taking advantage of the features of the last generation. How often does Adobe update their applications? You won't see the benefits of SSE4 until they do, so that newfangled feature may not exhibit any benefit to you.
If you're waiting to buy just so you can have a CPU named Nehalem, I can't help you. I never understood the people that freaked out because they didn't want to own a machine called a G5 if Apple was just about to release one called a G6. That sounds like conspicuous consumption to me and I just don't think that way...
I guess what I'm saying is: if you can wait a year to upgrade, you don't need a new machine.