Mary-Jo Foley has posted on her weblog that Microsoft has confirmed the OEM-status of the Windows Vista Media Center TV Pack 2008 update:
Statement from Ben Reed, Product Marketing Manager, Windows Media Center:
On July 16th, 2008, Microsoft released an update to the version of Windows Media Center included with Windows Vista Home Premium and Windows Vista Ultimate to our OEM partners - this update is referred to as the “Windows Media Center TV Pack”. In order to ensure that users get the best experience possible, this update will only be available from OEMs, as they are best positioned to provide the testing and hardware configurations for a great customer experience. This is due to the fact that in some geographies there are specific technical and hardware requirements for the Windows Media Center TV Pack that are best handled by the OEMs. We are working closely with our OEM partners as they finalize their decisions on Windows Media Center TV Pack products.
Read all about it at the source... I personally hope the team is still considering public release (altough no one actually ruled that out). Hopefull we'll see this appearing on Windows Update very soon!