HTML with embedded images is the only kind of HTML export that we provide.
We don't have plans for real HTML support right now.
What you are asking for could be done, but only for a subset of elements
provided by WireframeSketcher. Some of our customers create their own tools
to perform such an export. WireframeSketcher files use a documented XML
format that can be parsed and interpreted by such tools. There is even a
Java API that lets you manipulate screen files using a nice object model.
Let me know if you are interested in it and I'll send you more pointers.