Inoue is the hottest fighter in his division but IMO Donaire is the most popular, so Inoue would rather choose Donaire first for better fight revenue and a better chance of winning again. If in case Inoue will lose in the fight, they can set up a rematch or even a trilogy and both fighters will make money, if that will happen, Casimero might choose to move up in weight as he cannot wait for the winner of this two for years.
yeah right, better opponents with high amount of money that will flow within the fight. Inoue has that privilege to choose and like what you have said, Donaire is more popular after winning his last fight the money is much better if promoters will deal with it in the right perspectives.
And with how you assess Casimiros chances to fight Inoue depends if He(Inoue) take down again Donaire but if in case that Donaire win.
Casimero might move up instead of waiting, trilogy is very possible as again, money will flow more especially if the fight really brings more actions between Inoue and Donaire.