He already slowed down, his reactions to his fights against Inoue have shown it. He may have a power advantage if he goes down in weight division but the question is, Is he fast enough to connect them? I really admire Donaire but I have seen he is past his prime and most of his opponent is currently in their prime. Besides, wouldn't it put a strain on his body if he will lose weight past his regular weight limit?
No mate. Nonito Donaire is still quick and fast even at his age but it's just that Naoya Inoue is just quicker and too much for him. Believe me, Donaire can still KO and defeat other boxers in the bantamweight division. Inoue is just on another level and he is a monster in that division.
But we can't hide the fact that it might be too late to regain his position on bantamweight where his plan is to make some winnings first on a much lower level division. Even if he will be successful in the lower division, he might enter the bantamweight division obviously at a much older age.
And for let's say he managed to defeat those other bantamweights once he stepped up at that old age, I'm not sure if he can still repeat the achievement he done before fighting Inoue which is the oldest fighter to achieve a world title.
Maybe just making money as he feels he can still fight. Not a wrong move though before hanging his gloves.