Issue: Reset a User's Language when Navigating away from a Translated Article

This would be extremely difficult to do the way you are suggesting it because of the way vBulletin keeps track of the current language, and could also have users complain when the opposite occurs. I think a more practical method would be to allow changing an article's language using inline moderation from the forum view. Since no article is opened, the user would remain in the current language selection.

This would, of course, require an additional inline moderation tool to be developed.

That might well fix the problem. The only other thing I could think is to ask the article editor if they want to adjust language when they've created or edited the article.

This will no longer be an issue in 4.0.0 because wiki language is independent from forum language. See: http://www.vaultwiki.org/issues/2171/