Ive heard Errol Spence Jr./Terence Crawford to be the exact next that Manny Pacquaio will fight... just some humor & a slight chance to be the next. Actually I dont know quite yet who are these 2 growing professional boxers. But looking at their record are very impressive and Errol Spence Jr is a southpaw type of boxer also... could he be the next manny pacquiao? 
Terence Crawford is one of the dominant boxers today. Him being young and currently on peak has an advantage if ever he will fight Manny Pacquiao.
But I think he is playing safe and dodging any discussions related on his name being brought up as the next Pacquaio's opponent. He never showed an interest to the fight. He is one of the choices before the Thurman fight but just silent. And now that he just saw how Pacquaio gave dirt to the clean record of Keith Thurman, he surely realized that this legend still a big threat even for young boxers.