I've come to realize that too, it's better if he hadn't a rematch but that's it. Things were already done and I'm sure that there's no regret on him, Inoue is just better and nothing else with that. Donaire will realize that he's got a better passion to make and maybe he can go with coaching and training the new and aspiring fighters that shall rise under his flag. I'm assuming that he's just waiting for a great counter punch but it didn't happened, Inoue's aggressiveness got him with those punches that has entered on him.
The rematch with Naoya Inoue is the best match he can get. There's no other way since he already holds a BantamWeight title and to unify it, obviously, he needs to challenge those other boxers who hold the other bantamweight title. A title defense is not even an option for Donaire as he is catching the age already. He needs to get it done while his body is still cooperating with him. Unfortunately, that dream to become an undisputed champion in Bantamweight won't happen anymore.
Actually, Nonito Donaire can still fight even at his age and can destroy other boxers in their division. Naoya Inoue is just too strong for him. Either way, still a wonderful career for Donaire. If he will continue fighting or not, I will support his decision.