If Gaethje wins, 100% Poirier will be looking for that rematch. Otherwise Poirier might try to fight the winner of Dober vs RDA thats rumored to be happening. Poirier makes 500k to show and 100k to win and when he fought Conor at Lightweight both times and Khabib he got small cuts of the PPV breaking over 1m for all of those fights. I don't think Poirier wants to put his position at risk therefore he only wants to fight guys parallel to him Gaethje/Chandler/Diaz or above him McGregor/Khabib or a belt holder. Losing to a guy like Arman Tsarukyan would hurt his brand and earning potential pretty badly I think, he'd basically be out of the title picture forever at that point and put in a position of needing to take actually hard fights which he knows are high risk and lower reward.
Basically Poirier will wait, he wants nothing to do with Arman. What Chandler has done in the UFC and Poirier has done once reaching the top is textbook prizefighting, they know if you keep your name big and stay around the top even if you don't take hard fights or fight contenders anymore your name value keeps you in the que for potential title shots an you're never more than 1 or 2 wins away so they just circulate among eachother and like people. Poirier has always had horrible takedown defense too, why the fuck would he want to fight a 26 year old with a foreign name from Russian whos probably the divisions 2nd best wrestler?