Despite a loss, Dustin has nothing to be ashamed of after that fight and probably has gained a lot in the eyes of the fans and the UFC. Both gave a really good show. But situation in the lightweight gets a bit complicated. Islam wants to move up to face the winner of Leon/Belal, is not looking to fight Tsarukyan, but says he will if that's what the UFC wants him to do.
Poirier has announced his "half-retirement", meaning he probably won't be looking any regular fights, unless there's something on the line there. Since he's not getting a title fight anytime soon, this probably leaves only a fight for the BMF belt with Holloway, which would make sense as both had a great fight first time around. But I believe Holloway was set for a title shot against Topuria, so this might not happen. The other option I see for Dustin, is to get another high profile win against someone from the top 5, and hoping that Islam will lose to Arman (if they'll fight at all) and then he could get his final fight for the 155 belt against Arman.
You liked Costa vs Strickland fight? I personally dont. There were better fights in the card. In their fights I saw that Strickland mostly threw jabs and front kick (leg jab lol). And only in last round fighters switched on fighting mode. For me it was a boring UD by Strickland. In fact, wtf is with Costa? He used to be a brutal 1 round finisher, pumped beast that attacks from very start. Now his fights are long lasting fights, decision>decision>decision...
Yes, there were better fights but Strickland is showing his potential in each fight, he is awkward when fighting and it takes a while to get into the fight, but it is his game and it ends up being interesting to watch.