Apparently it is already available, as another poster, just earlier today,
posted that the CDs had been shipped to him with explicit instructions that
installation of SP2 was required "for legal reasons" -- which, translated,
means: "in order to maintain your license to use the product".
If the reasons are as suggested (and I have =no= information that either the
allegation about SP2 is true, nor the alleged legal reasons are correct),
then it'll be interesting to see how Microsoft responds to supporting Office
2003 SP1 systems.
Looking at the lifecycle page (
http://support.microsoft.com/gp/lifesupsps)
for service packs, I notice that Office 2003 SP1 has a normal expiration
date posted (October 2006), which is 12 months after the release of the
subsequent service pack (SP2: October 2005). So, there's not much indicative
there at all.