TRAC tends to separate wiki pages and tickets quite a lot, but there is definitely an argument for cross-reference.
I know that the TagsPlugin unifies both ticket "Keywords" and a new "Tag" list for wiki pages. I'm looking for a similar functionality for components and milestones. Is it possible with TRAC 0.11? If not, what about more recent versions?
Do I understand correctly, that you request/vote for tagging Trac resources milestone and component? This is reasonable, and could be done, because TagsPlugin is ready for tagging arbitrary Trac realms just by implementing the ITagProvider interface, i.e. by subclassing DefaultTagProvider, and you're up and running with the generic tag store in Trac db table tags as tag store.
Or is your request more about functionality like that provided by