Forgot to post this earlier. As soon as USUM were announced, many looked through /vp/ archive to see if there was any mention of the names Ultra Sun and Ultra Moon. And this was found.
Posted on March 28th, the poster had "USUM" as his name. When asked what USUM meant, the reply was that it stood for Ultra Sun and Ultra Moon.
As for the content of the post, it correctly predicted that USUM will be on 3DS, more Z-moves and Necrozma forms. But that was rather obvious and everyone was expecting that.
One other thing this post predicts is "New Pokemon". We have never received new Pokemon in middle of a Generation. That's a bit that makes it sound less credible. But that's common sense, and yet the poster still mentioned new Pokemon for some reason. Not to mention during the reveal of USUM, Masuda said USUM would "feature Pokemon that didn't appear in the original versions". Generation 7 has been breaking many traditions, like removing HMs, items like Bike and Gyms, so it might be actually true.
Still, nothing is confirmed, there's some worrying part about "new Pokemon" and the only things this poster got right were the names of the games, the platform they will be on and Z-moves and Necrozma forms. The only not-obvious thing were the names, even then, considering Solgaleo and Lunala are "Ultra Beasts", and Necrozma is also similar to Ultra Beasts, it's not unthinkable someone might have just guessed Ultra being title of the games. So make what you will of this. I'll just believe because it's more fun that way.
I'm guessing that got relayed to the rumored Switch version "Pokemon Stars", which will be announced in the E3 presentation
So a game was announced for Switch, A-chan. A game at least more than a year away. I don't know if that's the news you were hoping for, but there's something.