Zero. No chance. He won't win any electoral votes. Libertarians will need to start winning Congressional seats in order for there to be any change in the outcomes of these elections.
But you don't vote for the 3rd party thinking like that. It is either a look to the future (every vote builds on another) or it is a protest. Johnson is a bit of a goofball, but he was a good Governor in a very Democratic and diverse state (New Mexico). If you don't try and agitate a little, we will never get change. As a Republican, I think that is the first time I've used the word "agitate" about anything.