Will CH start a n XP Forever club?
The Microsoft Windows -> Windows XP section probably works out just fine, otherwise we would have 2 locations of similar posts for people with XP questions.
As far as the club goes... there is nothing stopping you from making this club website of your own on the web for XP at very little cost. I have doubts that it would be created at CH, since otherwise it would spawn off DOS, Windows 3.x, 95, 98, Me, 2000, Vista, 7, and 8 forever sections and the more sections the more involved the moderation is to keep out the spam etc.
Looking at the link you provided to this unofficial SP4, they should have gone 1 step further and made it to where it would claim to be SP4 in the About Computer section. Not sure how well protected this text info is to alter to have it specify SP4.