I don't think Conor is interested in a rematch lol.. That is even if Khabib will be able to fight again before 2020. NSAC is expected to come down hard on him (unlike Bones or Mike Tyson, he's not a big money making star, so they won't mind stripping him of his license). And if they do, UFC will be forced to vacate the title. They already set a precedent of taking titles off guys very easily.
Conor will be more interested in a GSP fight, or another fight with Nate if Nate is out of the title picture.
As for the title, look for a title fight between Ferguson and the winner of Nate vs Porier for the title once it's stripped from Khabib (or an interim title). THEN maybe we'll see Conor in the mix again