I hate to say it but we were right! Microsoft has officially released Service Pack 1 to manufacturing (RTM). Service Pack 1 for Windows Vista is FINAL! You can check out their announcement (a rather long one!).
As we have noted in this update, RTM does not necessarily mean a public release. OEMs would certainly start getting it this week and Microsoft would start making upgraded versions of Windows Vista. Fortunately, Microsoft has decided to be more forthcoming about when they would actually make the upgrade public.
So, Windows Vista Service Pack 1 is final and out there. It's just a matter of time before it's released to public, one way or another.