The next KDE 4 is expected to be available also for Windows. But even now we can see already a trace of KDE technologies on this platform: Swift the web browser. It's based on Webkit, which is based on KDE's very own KHTML and KJS.
The alpha release itself is not ready yet for prime time. It has bugs and rough edges and many stuff necessary for modern web browsing are not yet fully functional. But it's indeed a start.
Like its name, it's simply very fast.