The schematic apparently could be made by anyone with a basic electrical background and publicly available details on the Xbox 2. However, some key details are missing such as what type of RAM is being used and that the processors will be dual-core.
Either way, real or fake, it doesn't mean much to the average gamer. Who cares what's on the inside as long as the machine kicks butt in the end, right? What this does confirm is that there are a lot of people out there who can't wait to get an Xbox 2, including me.