They're just closing all the threads for character speculation. It was kept up an extra year because of the smash ballot, but it's a good time to put it away so it doesn't detract from boards dedicated to actual characters, like this one.
But if we did have to move, I guess I'd pick Bowser Jr boards. The Koopa Family has to stick together in such trying times. And I don't think we'll get any "lol, Zero says Bowser isn't a real character" attitudes from them. The worst place for us are the boards of characters that are really really playable, but the playerbase is convinced they're bottom tier. I can't theory craft with people who will not try to expand their idea of what a good character is. I'd love to do write ups for competitive Link or Marth, but I'm convinced everybody that plays them is on their death beds and simply won't believe they have a chance of winning.