I thought he would have put together another blockbuster for this summer. I think people can get behind one blockbuster fight a year, and dude is positioned to be the big name in that fight going forward.
Maybe he's waiting for the right opponent, knowing if he loses it means diminishing returns on these fights in the future, and if Mayweather won't get in the cage it's probably better that he fights someone new.
There's nobody at lightweight in the UFC who can carry their weight on the promotional side, and Conor is already the established champion, so it's not like he's got to fight for his legacy at this point. Maybe a GSP fight would be lucrative, since he can claim to be the best ever and people know who he is. Other than that, any return bout would be worth less than the interest he earned off the mayweather payday sitting out 2018.