Yes, it's all very hush hush. Which is why they publicly announced their plans to incorporate Flash Lite 3, Silverlight, and h.264 support almost four months ago. Follow this
link, but only if you are part of the Level 4 development team (it's top secret).
And, as others have said, it makes absolutely no sense that MS would release any kind of video drivers for HTC devices. The only thing that they are updating is WMDC for a few minor changes brought about by WM6.1.