In a post to the BCL Website question page, nfactorial inquired if there is a timeline by which the BCL (and the .NET Framework in general) intends to have full support for unmanaged APIs?

Nfactorial, we plan ot continue to expand the framework to have more and more managed solutions, and Longhorn will have a remarkable amount of managed solutions, exposing the underlying win32 APIs in many cases. The best way to enquire about specific APIs, is to find the appropriate Microsoft newsgroup, and ask your question there, since the appropriate Microsoft team will be monitoring the newsgroup. In your case of DirectSound, look for a Windows.Forms newsgroup, to see what there plans are in this space.