Future versions of Windows will be based on the same iterative process that has been used for past versions of Windows.  All of the  groups working on different parts of the system will incrementally work at enhancing their particular piece.  Certainly most new development will be outside the kernel in C# and based on .net.  The major addition to the UI will be the use of speech.  Over time speech will be supported at least for input in parallel with the mouse and the keyboard.  Support will be added to enable easier and more effective use of multiple threads.  The main use of this support within the UI will be to provide the processing power required by Windows to understand spoken words.