reasonably speaking, I think it will be the end of bitcoins, but looking to it in another way, That will probably be the end of the world as we know it right now if the internet as a whole "goes down".. Again there is no indicator for that and this question is the same as asking what will happen if the sun shuts down or anything like that.
The whole world is ran by the internet, if it goes down, so does everything in the world because we as humanity can only move forward, not backwards.