See the question and my original answer on StackOverflow

I suggest you have a look at Windows 8 and Metro Apps. Here is a link to start with this: The Microsoft BUILD conference, Windows 8, and the new UX Challenge. C# (.NET languages in fact), HTML5 and XAML are clearly the direction. Native C++ is back in town with WinRT. Silverlight is now in the gray area :-)

Even if you don't use Windows 8, it will give you a good overview of multitouch future in the Windows space.