I think their goal is to develop separate OS's for the business and individual user and to leverage out the power user and small business user who doesn't invest in the corporate client.
I don't think that's the whole story. I think Microsoft wants two major things:
1. Dominate the tablet market as they do the desktop market. Their plan seems to be to make desktop users get used to the new Windows UI on desktops and therefore demand the same thing when they buy a tablet.
2. Get 30% of *every* single 3rd party application that will ever be made without even lifting a finger, like Apple does with their App store. Since Windows is pretty much an open platform, the only way to accomplish this is to force users into a different closed platform where software vendors can only sell through Microsoft (and are forced to buy Microsoft tools to develop applications in this new platform). Enter Windows RT and Metro Apps.
It won't work, of course. They seem to have forgotten three things: first, the only reason the PC succeeded was because it was an open platform, both in terms of hardware as well as in terms of software. Second, Apple is only able to get away with what they are doing now because they were a closed platform from the very beginning *and* because Steve Jobs had *taste*, something Microsoft NEVER will (just look at how ugly that Metro UI is).
Windows 7 got very close to being a beautiful UI (as its success proves), but instead of learning from this, Microsoft got greedy and, once again, decided to go on a totally different direction.
The only consolation I have is that I am pretty sure a very large percentage of Microsoft employees disagree with the direction Steven Sinofsky is taking the company. I bet they secretly wish Windows 8 to be a HUGE flop so they can turn things around again... and Steven Sinofsky needs to learn a turtle neck and brisk manners does not a Steve Jobs make. You need to have an innovative vision *and* good taste too.