I have four languages on my blog, this works without any problem. I just created a category per language. These categories are published on theire own page. So i also have four pages. You can simply create a new template for the page.php so every page with it's own language has it's own header in that language.
However, when the visitors clicks on a headline it will always use the same single.php thus that page can only be one language..
Is it possible to have multiple templates per single.php just like page.php has?