Windows XP SP3 Postponed Until 2008
Rockgod quotes an article saying "With Microsoft now saying that its next major service pack for Windows XP will not ship until 2008, some Windows users are wondering whether the software upgrade will ever be released." and then later "Michael Cherry, an analyst with Directions on Microsoft, agrees that Microsoft may very well decide to drop XP Service Pack 3. "It absolutely could happen. Microsoft is under no obligation to produce any service packs, ever," he explains. "They feel that because these fixes are available through the auto-update that there's less need to create a service pack."
They killed Windows NT 4.0 SP7 in the ßeta process
They killed Windows 2000 SP5 in the pre-ßeta stage
Given this track record of killing off Service Packs shortly before they are released, as some (including me) might suspect in an effort to drive adoption of their newer software (which makes them money unlike a service pack) I'll be extremely surprised if Windows XP SP3 is ever released.
IMO, what they are saying now is just lip service/stalling and they have already made the decision.
Actually, even Joe Sixpack is pretty tired of crashing spyware ridden computers. And the very moment they see another option, they are sure to at least look at it. And with Vista's new hardware requirements likely not matching their current hardware, there's yet another possibility he will look at his options before buying a new computer. Apple has become rather affordable as of late and their reputation for being easy will do a lot in the way of bolstering confidence. And if he actually talks to someone and finds that a mac can also run Windows, he'll be sold.
That's a lot of IFs, and I don't expect a huge number of people to fall within those cracks, but I think the numbers will increase and become rather noticable.