So far, the only thing we know about a Pokemon game for the Nintendo Switch is that there will be one. Most people are suspecting the greatest amount of information will come from either this year's E3, or the "close to E3 Nintendo Direct" that the company is so well known for. Though an official Nintendo Magazine appears to give us a taste of what to expect.
Discovered by Twitter user raqueruu, they posted photographs of the Spanish edition of Nintendo Magazine. The section contains snippets about all of the upcoming games, including Pokemon. Said section indicates that Pokemon for Nintendo Switch will be the eighth generation to the series. It also remarks on how the company will be rethinking the series, planning to surprise players with new mechanics. We can expect more on the game later this year.
New generations are no joke. This would mean a new land, full of new Pokemon. Each console normally begins with a new gen, and this would be the Switch's first Pokemon game. So it fits. Each generation also implements new mechanics, so this isn't that surprising. The question is what will those mechanics be? Things like super EV training and egg hatching have been fan favorites, while others have been not so fondly received.
This information should be taken with a grain of salt, however. The magazine in question, despite being an official source, has been wrong about Pokemon titles in the past. Something to consider before committing the information to heart.
We know a Pokemon game is coming, and it seems unlikely that they'd have the Switch's first Pokemon game be a port or remake. Now the game after that, I could absolutely imagine being a Diamond and Pearl remake.