If we get to know everything there is.....what then?
Don't worry; that is highly unlikely to happen in your or anyone's lifetime.
Some idiot back around the turn of the 20th century said the patent office was no longer needed because there were no new inventions to patent. A 1940s IBM executive thought there might be a worldwide market for at most a couple dozen computers. Bill Gates rues the day he said no one needs more than 640k of RAM, because what would they do with it.