Hmmm...
View attachment 31158
(Still hidden away in the current leaked build, but it is possible to launch it.)
This will change over time. As the OS evolves, so will the API. They didn't migrate those applications because the Metro API is not ready for them yet and doesn't support all the functionality they needed. Once the API evolves and supports the functionality, these apps will get converted. Then that also means the API will be ready for other big apps like Photoshop and Matlab to be converted. This will all happen along with phasing out the desktop, but it's a little further down the road.
And remember, not EVERYTHING will be cross platform. There will be metro apps that only work on desktops and not on tablets or phones.
I'm in engineering and I can easily say that all the design tools I use will NEVER be ported to Metro. Heck, most of them don't even support Win7 all of the way yet.
There will always be a need for command line windows with the stuff I do. The design tool programmers will move to Linux before they port to Metro...
You can already create a Metro app with C++/DirectX so you could entirely replicate a Windows desktop GUI if you wanted. But that's not necessarily the best approach.
Windows 8 the OS is independent of the "type" of machine you use it on.
So, both.