To make Google and other spiders crawl our translated web pages it could be possible to add other languages in sitemap.xml
Now it's impossible because language selection is done with accept-language (and google disables it on its spider) and browser cookie (disabled for search engine spiders), and the user can change it via POST to set_language (according to http://docs.djangoproject.com/en/dev/topics/i18n/#the-set-language-redirect-view )
If we enable also GET set_language, it could be possible to add translated pages to sitemap adding to all translated urls an ?language=en
Otherways Google sees only a portion of an i18n web django web site, with a lot of performance loss.