Axiom Verge 2 is coming next year, it was announced during today's Nintendo Indie World Showcase. It's expected to release in "fall 2020" (that's spring in Australia) but we only have confirmation that it's coming to Nintendo Switch. That said, it'd be hugely surprising if the game remained an exclusive there.
Aside from the trailer and launch window, there's not much else in the way of firm information: the game page (opens in new tab) on Nintendo promises "completely new characters, abilities, and gameplay", and the same lush pixel art is present, only this time with a more naturalistic, snowy theme.
It's good news: the original Axiom Verge was a nice modern tribute to Super Metroid, with our reviewer Andy describing it as "old school, but with a modern edge".