Someone already could deploy the user interface of their application using HTML/CSS, using either the awesome IWebBrowser2 COM interface from Microsoft, or the Mozzila Browser.
Norton Antivirus is using IWebBrowser, Skype i think is uzing Mozzila's...
Applications like Skype could never be developed using anything else than the perfomance of native compiled C/C++. And if not compiled, they could never use tricks to stop you from debugging Skype...