Eurogamer says that development paused on Stars while the team at Game Freak was wrapping Sun and Moon, but now that those are in stores work has resumed. This won't be a simple port, from the sounds of it. The game will feature high-res graphics and new bits that aren't in the new 3DS titles. What's more, you'll apparently be able to trade creatures back and forth between the console and handheld version using the Pokémon Bank mobile app. There's also the chance for new Pokémon in Stars that aren't available in Sun and Moon.
The main Pokémon games stick to handhelds because they're made for battling and trading on the go with friends. As the sizzle reel from October made obvious, the Switch is in fact a portable console, so the design philosophies from the 3DS games shouldn't be a roadblock here. If you're hoping to play the game next March when the console is scheduled to release you're going to be out of luck: Eurogamer's sources say Stars won't be out until sometime later in 2017.
Earlier this year when two of our editors faced the question of whether or not the series should move to consoles, Senior Editor Aaron Souppouris had this to say:
"Almost 30 years [since Red and Blue came out] and we have the ability to make Pokémon games that look, sound and feel better than the original animated series. And we're not doing it."
With this rumor, it looks like we're one step closer to that happening.