It's already out on MSDN.
http://www.microsoft.com/presspass/press/2005/oct05/10-14DigitalLifePR.mspx
[snip]
Using the built-in Media Center Extender technology of Xbox 360, planned for availability Nov. 22 in North America, Update Rollup 2 will connect Xbox 360 to a Media Center Edition PC, offering instant access to thousands of on-demand movies, music and videos available on the Media Center PC, and enabling users for the first time ever to stream high-definition content from Media Center PCs. Update Rollup 2 further builds on the Windows XP Media Center Edition 2005 experience by delivering a set of performance improvements and new features that enhance Media Center, including the following:
* DVD changer support. New integrated support for external DVD changers will enable consumers to watch movies and manage up to 200 DVD selections from the Media Center interface. Media Center will display information and cover art for each movie loaded in the DVD changer. Media Center-supported DVD changers will be available beginning this year.
* Away Mode. Away Mode will bring the convenience, quiet performance and instant on/off functionality of consumer electronics to Media Center PCs. Away Mode improves upon current PC power-management systems by enabling the system to silently perform unattended tasks — such as recording TV shows and streaming content to Media Center Extenders — in a low-power mode that makes the PC appear off. Away Mode will be available on select new Media Center PCs in upcoming months from partners Acer Co. Ltd., Fujitsu Siemens Computers, Gateway Inc., HP, Phillips Consumer Electronics, Samsung Electronics Co. Ltd. and Shuttle Inc.
* DVD-burning improvements. Updates to the Sonic Solutions DVD burning engine will improve the performance and capabilities of DVD burning in Media Center Edition. Consumers will be able to convert high-definition TV shows to standard definition and burn to a DVD all in one step, as well as burn to a DVD from other PCs on their home network.
* Additional HDTV tuner support. Update Rollup 2 adds support for one more HDTV tuner, meaning it will support up to four tuners: two analog and two ATSC high definition. U.S. customers will be able to use two NTSC (analog) capture boards and two ATSC (digital) capture boards. This will enable personal video recording of two shows at the same time, broadcast as either ATSC digital TV (480p) or high-definition TV (720p/1080i).