Ok, Misty was replaced due to sexism. They wanted a girl whom they can change into Swimsuit options and be considered eyecandy for some people. Basically, if you're a female character and you aren't garnering sexual eyecandy, that must automatically mean you're useless. Masamitsu Hidaka said they replaced Misty BECAUSE they wanted give males eyecandy, and they can have them wear swimsuits. It also explains why they initially gave May a huge chest and why Dawn currently has a short skirt. I've never really trusted Masamitsu Hidaka, but the fact that they never even bothered to replace Brock at least when they would have had a good reason to (as he fared the worst in Johto), they gave May and Dawn several shots in Bikinis/swimsuits (and in the case of May, got them in 3/4ths of her movies, and even went as far as to "pseudo-strip" [you know exactly what I meant by that].), not to mention their airheaded personalities that are shallow compared to their body (similar to Love Hina, in one sense) seems to hint at that being true. Heck, even BEFORE the interview, I had predicted that Misty was replaced for those reasons alone (or at least that they didn't replace her for stality issues).