I have to strongly disagree,because Mistys story is far from being resolved.She is a character left with a lot of untapped potential and in my opinion her return would improve this show and make it more interesting than it is now.
Misty story is resolved. She wanted to train powerful water pokemon. She is now. She wanted respect from her sisters. They give it to her. She wanted to be surrounded by water pokemon every day. She is. She has no loose ends in her storyline and has nothing to gain by returning.
About her goals being achieved this is also incorrect because her goal was to become water pokemon master and not a gym leader.She never showed any interest in becoming one until her sisters left leaving her without a choice.
Being a water pokemon master would logically involve training and battling with water pokemon for a living whilst in a position of authority. Misty is doing this.
This can be answered in two ways.From anime perspective the reason why she still didnt left the gym is because she doesnt thrust her sisters enough to leave it in their hands considering how they like to give badges to trainers without having them to actually battle for them.
This is somewhat true, but it's also clear that Misty loves being a gym leader. She does not cry herself to sleep and claim to be trapped there. She could leave whenever she wants. She hasn't and won't do it.
One more thing i never found any of Mistys pokemon uninteresting.Sure some of them like Goldeen or Horsea didnt received much spotlight but if she ever returns to the main cast im sure that writers would handle them much better than they used to.
Swinub. Staravia. Sudowoodo. Pachirisu. All pokemon from the current saga, all of them lacking in screentime, all of them with more potential than Goldeen and Horsea. The writers have improved, but they still struggle to balance screentime.
By the way i know what has been said about Misty in that interview,but i didnt take those words as "set in the stone".That statement about her never returning to the main cast was stated by former pokemon director who is now a storyboard artist and NEVER by pokemon writers.
He works on the show. He may not be a writer but he has some idea of what is planned. If he were a janitor or the lunch lady I'd agree. But he's not.
As for Brock i know that people want him gone permanently,sadly.I was just saying how i wouldnt want that he leaves forever but only for some time.I understand that people want break from him but in my opinion it would be unfair that he leaves forever.His character doesnt deserve this at all.
Brock will have cameos and return episodes like May, Misty and Tracey have had to varying degrees. Some might say his character deserves more than what he's getting, given how good he was in Kanto.