we currently have an open ticket to add a site map generator. Its on the list for 4.1 but cant say for sure it will get in.

If you give google or other crawlers, the forum url, they will find all the posts. If you use the wp plugin for google sitemap generator, when the bots crawl they will find the posts.

Still, we want to add this in too.

Might be a good tip. The global translator plugin works hand in hand with the xml sitemap plugin. You might be able to borrow some code from this one;)

http://www.nothing2hide.net/wp-plugins/wordpress-global-translator-plugin/

http://www.arnebrachhold.de/redir/sitemap-home/