I mean, this is not true at all, it's been going on forever, even post-SSB Kaio-Ken, otherwise you wouldn't have people that get tired of explaining otherwise. Neither do said posters do it in a civil manner either (When's the last time someone asked something like "Do you think Super characters be in this game?" There'd be no good reason to be hostile towards a post like that.), the majority of the time it is clearly meant to get a reaction out of others, even when they actually aren't aware that Super content is already in. On one hand, yes, we should not fall so easily for the obvious bait, but nevertheless, they clearly know what they're doing.
It's the same people saying the same thing and it's always the same people responding to the comments. At this point I'm going to put the "there won't be any Super content in the game" people in with the "yes there will, how can you-" people. If people are so defensive towards Super comments that they fall for that bait I'm just putting them in that same category. Same with the people childish enough to make posts like that in a videogame thread.
Shit's overall childish.