wow good on them! At least in this case, you it seems easier and more likely people find a clown fish at a LFS than a blue tang. Obviously there will be some in stock, but numbers wise not nearly as many. I am sure demand will go up, but not by as much as what Nemo did. Besides, it isn't like Dory didn't have a big part in the first movie to begin with.
Edit. Also, prices should go up. I wouldn't consider that unethical or anything, but there are only so many blue tangs to go around. If demand increases and supply doesn't, or doesn't increase as much, basic economics states prices go up.