Okay, I could understand that giving out a Sinnoh hat Pikachu would by itself not necessarily be indicative of anything. But everything else considered, this just fucking seals the deal.
The huge lack of Sinnoh Pokemon in the Alolan Pokedex.
The references towards Palkia, Giratina, and Bronzong.
The Munchlax that was released at the launch of SM, which is very similar to the Torchic that was released at the beginning of XY.
The strange storybook video in which the Sinnoh starters took front stage as main characters, and the rest of the Pokemon in the video were still predominantly Sinnoh Pokemon.
Behind Plumeria and Guzma's battle intro, the primary colors used are Pink and Blue, colors heavily, HEAVILY associated with Palkia and Dialga respectively.
The fact that Lucario and Piplup, the Sinnoh regions two MOST POPULAR Pokemon, are two main character Pokemon roles in the upcoming movie.
The fact that Sinnoh is officially 11 years old from Japanese release date.
And the biggest fact, that the key items of the Sinnoh games are found in the code of Sun and Moon.
Anyone who still thinks they can refute this either is doing it to be contrarian or has some serious cognitive dissonance going on in their head.
Sinnoh Remakes are about to happen, whether or not you want them to. Get the fuck over it.