It's all very complex - and I guess we shall never have some ideal solution that will work for all purposes - but I believe we should experiment with different settings.
The integration solutions that I've seen thus far are mostly about adding some forum functionality to wikis: a discussion page paired to a 'main' page (on wikipedia), a 'attach to page' method that adds a comment to the wiki page with some special visual style that makes it different from the other content. But there can be many more ways of doing that integration. In particular I see many ways of doing it the other way around - by adding wiki functionality to forum sites and letting it's users:
- edit the list of subjects just like they would edit a wiki page
- 'overwrite' a part of the conversation with a summary that would be a wiki page, editable by all the participants in the overwritten part of the conversation with the expectation that it will contain a consensus between them on what was written, the overwritten text could be available behind a link
- edit some small 'pagelets', or menus used for navigation (with more and more screen realestate we can add more of them)