Okay so it’s just a though, but if season 3 will starts with a struggle about who’s gonna be the pilot of Black, and the obvious choice would be Keith or Allura, but the lion don’t let them in. In the mean time Lance starts to lose connection with Blue which leads to the arc of Lance and his insecurity.
What if he would thinks he is really not needed and Blue rejects him, with this and his constant homesick he decides to leave the team since Zarkon is defeated there is no need for voltron anyway even if they find Shiro or there would be a new leader (and they don’t know that Lotor is coming
). But when he is up to leave in the hangar the Black lion activate itself and let him in.
Sorry about my english and the crappy image editing, but it was a sudden idea, i had to write it down quickly. :D