Depending on who you listen to, they're between one and fifty million years out from Earth. Even assuming the ship was taking the scenic route while it was unmanned and it could plot a more direct course back to Earth, it's still going to be a long damn time before they're anywhere near Earth. And that's not even counting the fact that the Destiny gates aren't galactic-range like the modern ones, so they'd have to practically be on top of Earth to make a connection (without a power boost, of course).