a 'single library' on a Windows machine is just a bunch of shortcuts. not that different from the shortcut icons for games I own from different storefronts on my desktop, just more 'handheld friendly'
my reasons for doubting all this have to do with MS making a device that could potentially use none of their services. their digital storefront, and charging for online/subscription services, is their money maker. and if the solution is some kind of locked down PC, than that's just another console
maybe I'm wrong. time will tell. if MS moves away from charging for online, it will be interesting to see how Sony and Nintendo react