I think that quite contrary - when language without literature is lost then everything about this language - traditions, knowledge, history, is lost forever (unless anthropologists manage to save some bits of it).
Not nessasarily, the people could continue to pass down the traditions/knowledge/history using another language. If a language with literature is lost, then you loose just as much of those things, as well as the literature (because no one can understand it). Of course, having literature increases the chances of having a rossetta stone.
