Language is an ever-changing, fluent thing. Many different languages have come and gone like Sanskrit and Latin and even the current languages change massively over large periods of time. How many of you can understand every passage of Shakespeare? It's the same language that we are speaking here but I'll be the first to admit that I have no idea what The Bard wrote down most of the time. Hell, I wonder if an English-speaker of 20 years ago would understand some of the crap that goes down on Facebook, Twitter, and chatrooms today.
The point of my rambling is this: Language changes. New ones come, old ones go, and there is little you can do to stop it. We can choose to save the "dead" languages but for what purpose in the long run? There will never again be a need to speak this language.
To wrap up: despite my ramblings I do believe that we should, as oppp7 said before me, "archive" the dead languages but I see no real purpose in doing so other than preserving the last little bit of a culture that's dead and gone.
I apologize for not being more organized with my thoughts; I'm a little out of it today.