Of course if you turn a game console into a PVR, it needs to be able to record two (at least) shows at the same time while it is playing a demanding game. If not then it is worthless as a PVR.
My understanding is that the leaked Xbox.Next info shows that it can do that. Maybe it has dedicated hardware for that so that it doesn't slow down any gaming activity.
I also feel the Xbox should stay 1st party. Allowing OEMs to create Xboxes will just result in the overall Xbox quality decreasing.