Hi!
Microsoft has released something like a mini service pack with the start of Windows 8 (see
MSDN Blog and
KB2756872). However, I don't think that this makes 500 to 600 MB.
Heise writes, it would be around 170 MB.
Have you looked, what else was downloaded by Windows Update?
I would guess that Torsten Wittrock is already working on an Win 8 integration and will release it soon after the public availability of Windows 8. Depending on the catalog contents, you then could add this and other non-security packages to the repository with static links.
Gerby