>>31324432The actual reason they don't make any balance changes mid-generation is actually because of Nintendo keeping them from doing that.
Nintendo still refuses to accept that pretty much everyone has an internet connection at this point in time, so they forbid big patch updates. They don't want the people who don't have internet to miss out on content, so bug-fixes are pretty much all you can expect. GameFreak originally created the "third version" to get around this.
Smash Bros. was an experiment in trying to inch their way out of this way of thinking, so maybe it'll change in the future. 