I know that this has been asked several times in the past already, but I thought I'd ask again, just in case you happen to have some development time to spare. Would it be possible for you to find either an open source, or (affordable) paid DOCX > HTML converter, and integrate it into a proper previewer in CT?
It's not too much of a pain for me to convert my source documents into an HTML file before starting a project (using Click to Convert 6, which is probably the best you can get at the moment on Windows) – although it can be a bit of a pain if the project involves multiple files – but I think that all of this is probably too much to ask of your average newbie / not very technical user, who is then effectively left without a previewer.
Any plans or news in this regard?
CafeTran has a very good HTML viewer built in but the conversion from the native application file format to the HTML format is best handled by that application itself. Almost all word processing or DTP apps have this option. For example, both MS Word and LibreOffice can convert .docx easily. Please see it here. It is only a matter of saving the file as html. It is very easy to produce HTML for the preview in CafeTran on each operating system. However, some options to automate the process from CT interface may be investigated in the future if the native document's application makes it possible (via command line, for instance).