^^^ I have see the latest movie, and how they were canonically confirmed to be sisters...but to be honest that's hardly surprising now. Fanon about how they're related is already old news (Thanks Game Theory, and if I recall correctly they were even speculated to be mother and daughter in that scenario), so it wouldn't really produce that much drama except for those who really cared about shipping these two now but are really against incest.
But it's not stopping the enjoyers anyway lol. I for one am glad that there's still good Yuri art of these nintendo girls~
Also quick vent, that "movie" isn't what I would really call a movie. Sure, it's really fun to watch and the style's really cool but the story behind it's just shallow.