Of course, Donaire will take it seriously as he can't afford to lose the opportunity to have a rematch against Inoue, if he loses, I doubt Inoue would still give him a rematch when he doesn't have the belt anymore, it will be Casimero vs Inoue if Casimero would be successful in defending his belt.
If Reymart Gaballo doesn't get anything in their current training then the serious Donaire will finish him in the early round because he is not his priority right now. This kind of fight before the dream match would be good as well because if he ever sweeps this win like he usually does, the fans want to see him fight the best in his weight class which is Inoue or Casimero. seriously, those two should not be fighting other boxers other than best fighters like them.