The voting isn't necessarily about popularity, there's a lot more to consider than just popularity when choosing a new fighter to the roster. And really choosing anyone from the ballot is technically "fanservice", since even if just one fan asked for a specific character and that would end up being added to the game, it still would be "fanservice". Again, we are only suggesting characters, not voting for someone to "win" with the most votes.
Sure the most logical thing to do is to use only the most voted characters for "maximum" profit, but since when has nintendo done anything to get the best profit? They've even said that their not interested on getting "whales" or anything like that to maximize profits with their coming mobile games. (Sure it's possible that they're just saying that without meaning it).
Also they've said that every voted character will be considered as a new fighter and I wouldn't be surprised (let's say that they would make 5 characters from the ballot for this example) that they would make 2 from the most popular ones, 2 from the between and one from the lowest voted as characters. I mean hey, maybe that one character that happened to be voted a low amount was such a great suggestion that Sakurai himself thought (and everybody else in the team) that it would be a fantastic addition to the roster.
I'm not saying this is how it's gonna go, but I certainly wouldn't be surprised. Saying "this characters is automatically in, because it's the most popular one" is most likely only going to get you disappointed in the end. They didn't add Wii Fit Trainer to smash because people wanted her/him. Just saying. (Sure you can argue that the situation is different because we are talking about a additional character that's gonna cost on it's own, but I'd still say that no character is"sure" choice for the devs of smash).