That's too bad. As popular as Misty is, I feel like the anime could have been "revived" for the older PokeMon-loving audience if she came back.
a) Brock is awesome: Fact // Brock's character was ruined: opinion x)
Simply put, it's possible we may see a return of her character just as much as it was possible that Brock made a long return. There are many spontaneous episodes in Pokemon and I wouldn't ever put it past the anime producers to randomly make Misty show up in say a tournament and start following Ash around again. The "writers" as you will are well known for bringing just as many unnecessary plots into the anime as they are for bringing necessary ones (to follow said VG).
Unlikely? Probably
Will she ever return? Possibly
Would it ruin the anime? Unlikely
Would people keep watching it? Certainly, it's Pokemon
So we'll never get to see Misty and Ash hookup? Bummer...
Can always hope for a epilogue special or something at some point. I wish they just went with new trios or kept the same trio--it's never really been the same for me.