I just released an upgrade to Wikipop, my WordPress plugin. I had a number of requests for the plugin to support Wikipedia languages other than English. I added a popup window in the visual editor that allows you to select your language, and if you want, search Wikipedia for text other than the text you're linking. Check out my plugin page for the full changelog and a link to the download. If you already have Wikipop installed, you can just upgrade automatically from the WordPress administration panel.