I don't think that the concepts of Javadoc are outdated. As far as i can see, these concepts are rooted years ago in a product named doxygen, which is still available for other languages (i.e. Objective-C where it is heavily used). Even this has it's predecessors - have a look at the programming environment used by Donald Knuth to create TeX (Literate programming).
Nevertheless it is a intriguing idea to have a single source for program code and documentation.
Besides of that, the presentation of the documentation can be customized to your special needs using a plug-in system supported by the JavaDoc tool. You might provide a plug-in (as we do) that publishes directly into a database which is directly accessible via web. Using collaborations anyone can provide additional comments or clarifications to the documentation that might find their way back into the original source.
