Well, it would seem an eagle-eyed person by the name of PeDaRoYs at Marioboards (and LukA8 at our forums for pointing to that!) spotted that the official Rio 2016 blog accidentally posted at least three new screens of the game, which were quickly removed moments later.
Luckily, the urls still work, so the three shots are still viewable below:
The user also spoke about other screenshots, one of which apparently shows Rosalina:
Other photos were:
-Sonic competing in Archery
-Zazz (against Yoshi) preparing to serve in Table Tennis.
-Rugby 7s with 3 Marios, 2 Sonics, Diddy Kong, Boom Booms and Egg Pawns
-Rosalina, Daisy, Peach and a female Mii competing in Synchronize Swimming
Hopefully the other screens will be found soon enough, but if not, E3 is only a bit over a week away where we’ll know much more!