Misty has no chance of returning to the cast at all, her storyline has been resolved and the writers have stated she will not come back. And nor should she. Misty's water typed teams resulted in highly unused and uninteresting pokemon such as Goldeen and Horsea. No type needs any more exposure than any other and water pokemon are prominent enough as is. Misty has already achieved her goals, she has nothing to gain by coming back.
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.
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.
Maybe she is a gym leader now,but if she ever wants to achieve her original goal she will have to leave the gym for some period of time and start travelling again because her dream cannot be accomplished only as a gym leader.I see her position of being a gym leader more as a stepping stone which willl on one part help her to achieve her ultimate goal one day.
Now it comes the famous question "but if Mistys goal isnt to be a gym leader than howcome that she still didnt left the gym?".
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.
From real life perspective writers decided to cement her in the gym without giving her a chance of achieving her goals and it seems that they arent planning anytime soon to return her in the show.
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.
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.
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.