Well not everyone necessarily cares for Krystal, meaning that I don't think that much hate will be on her if she is announced.
The only ones who will cry about it most likely, are the people who already have issues with her for whatever reason and those (if Wolf doesn't return) who will feel like she replaced Wolf.
How I see it is that people will get mad at the devs and Sakurai for not including the character they wanted, but of course some of them will start attacking those who got what they wanted and bash the characters that got in, it's unavoidable.
These types of people are just pure ignorant and don't know, nor do they wan't to know, how things work and that's why they will just b*tch and moan about everything.
You can easily see it from the amount of hate the clone characters in smash 4 get (Lucina, Dr.Mario and Dark Pit) and how they think those should have been just costumes. They somehow think that if they were costumes, there could've been another character that wasn't a clone, even though no one in the dev team has ever said anything like that. The clone characters were added as a quick bonus, they didn't replace anything, so this thought that "they should've been just costumes" is ridiculous. Why in the hell do you want less? It's like saying "someone gave me 3 dollars even though I only needed 2... what a f*cking *sshole!". -.-