With the Current Windows 7, Microsoft has made some bold moves away from Vista, when not along ago, they were doing double time to supposedly do 'damage control' on Windows Vista. To show how awesomely spectacular an OS it was.
Windows 7 is a ground up reworking to repair the "holes", as you know"S", with Vista in general
I got word from a good buddy who is doing IT with input from MS sources, presently MS plan to shift focus more squarely on Windows 7, in effect dropping support for Vista OS sooner then it will for XP.
Nothing is too etched in stone, but MS will extend SP3 expanded XP installs into 2020 perhaps, at least a much longer stay of execution as previously thought!
XP is so popular with most folks, it may even return to store shelves at retail! MS is considering this, due to the large pickup it saw in online demand. I have this from a trusted source, so we shall see what plays out.
At the moment, you best install the Service Packs or the MS online support of anything not updated...won't suffice