You're right to be concerned. Those pages in other languages will not be indexed unless there are links pointing to them. You might try submitting an xml sitemap, but without visible links in the pages, even that is not likely to get your translated pages indexed fro very long.
Thanks for the reply, I did some more reading though. Does your answer imply that you disagree with the last post in this thread: [webmasterworld.com...]
In any case, I find something that seems so straightforward as a multi-lingual site extremely difficult to comprehend. A lot is said about it in blogs and forums, but I have yet to find a solution which is both maintainable (from a designers point of view) as well as workable (from a users/bot) point of view.
Google indexes the url. A different url is a different page. Googlebot will not do content negotiation with your server the way a browser will.
And second, unless there are inbound links to a url, googlebot will often not find it at all. Even if it is found by some other method, such as a sitemap or direct submission, it still need some inbound links to "stick" in the index.