If MS have any sense they'll make a limited user account by default - this will make it a lot harder (if not even damn near impossible) for viruses to infect the system. Shitty old Windows programs that won't run correctly without admin rights can be run thourgh a compatibility layer.
It's all part of their strategy. Limited users cannot be properly tracked and spied upon. If Microsoft chooses not to plug a hole, it's probably because Microsoft is using that hole for its own purposes.
But seriously, user accounts, limitations, and permissions get in the way of a dumbfuck's normal computer usage. GrandpaAlzheimers, JimmyIlliterate, and SallyShoulderpads, who can't be bothered to learn security, would cause a lot of system damage by trying to get around limits and permissions. So Microsoft has to keep everything wide open in order to maintain its user base. Smart people, as usual, get shafted. That's why many smart people have found a way to live without Windows.