We know that Khabib wants to defend his title for the first time somewhere at the very end of the year. We are quite sure that Conor won't fight Khabib in the Octagon. We are also fairly certain that Ferguson won't be ready to fight until somewhere in 2019 (but you never know with that guy).
That leaves us with Poirier, Alvarez and Lee who all claim to have earned that title shot. Sadly, the guy with the best claim to the shot (Poirier) is the easiest matchup for Khabib.
However, since Khabib will fight in December, that leaves room for another fight to determine who gets the shot. Since Alvarez had a disastrous title defence against Conor and is ducking Poirier, I say make Lee vs Poirier somewhere in August to determine the challenger. Keep Alvarez on standby if one of them fails to make weight or gets injured.
Problem solved.