Re: The next generation will attempt to port the kernel to Javascript...
You do know that multi threaded programming has been fully possible in C right from Windows NT 3.1, not to mention OS/2 in the 80s? (Although the file dialog is written in C++, and calls a lot of interfaces).
Microsoft are not stupid, and each new release of Windows has been optimised beyond the previous one (Yes, sometimes this is accompanied by a lack of flexibility or functionality, or increase in requirements in other areas).
If the file dialog doesn't populate bit by bit, there's a reason for it.