We really don't know yet, but if we look at Inoue's frame, he could easily add 4 more lbs to his frame or he could be walking at 126 lbs or more in off season so I think there will be no problem for him. And the power though, he could be more powerful when he goes up in weight, similar to Devin Haney wherein he was not known to be a big puncher at 135 lbs, but when he moves to 140 lbs, he knock down a supposedly power puncher in Regis Prograis.
Inoue's team mentioned before that they will take 2 to 3 title defenses and then they might consider moving up again to 126. I am also expecting Inoue to move up in weight next year.
The difference though is Haney is still young and he just moved up in his second weight division while Inoue already is 6 divisions above once he enters 126. But it should be doable. However I guess 126 is Inoue's final division as he is already in his early 30s. It will be more risky to continue moving up in weight while fighting bigger and heavier opponents.