I believe the rumor has been checked from several credible sources if I remember correctly, so it's looking likely. Seems like the perfect fight, if Gaethje performs well he's only 1 or 2 wins max from a title shot. Johnson has the skills to let us know exactly how good Gaethje is, without it being too much too soon for Gaethje. The fight makes sense for both Gaethje and Johnson's careers while it really doesn't for Barboza, Ferguson or Khabib.
Just my 2cents. Listened to Gaethje on the MMA hour, he's extremely honest and genuine....You don't get that very often in the sports world, especially not combat sports.