I'm assuming you could set up the multi-site option and mirror your content, because using subdomains like you how you pointed out you would not use the same database.
The other option is to just use some type of multilingual plugin that allows you to show the same content in X amount of languages. You can find out more information about this on WordPress: http://codex.wordpress.org/WordPress_in_Your_Language
and here http://codex.wordpress.org/Codex:Multilingual
Hope that helps.