One of the things said during the keynote was that trying to come up with a complete replacement for Win32 in WinRT was too much for a single release, so the initial focus was on Metro. Which is why I think it's to be seen as the start of a clear shift in direction away from all the legacy tools whether they be WPF, Silverlight or Win32 itself.
For desktop applications it's probably worth considering if they can be 'reimagined' with a Metro style UI. Obviously that won't suit every application and for those that really need to be tool heavy (like Photoshop or Excel) it's probably going to be a case of keep doing what you're doing for now. However starting to think about newer WinRT concepts and keeping them in mind when planning for the future is almost certainly a good idea.
It's also probably worth betting on the Ribbon UI, it's integration with Explorer will not only make applications feel more native but if I were a betting man I'd imagine it's the way WinRT desktop apps will be expected to expose their UI.