The Sonos One is getting an internal component update, which means Sonos One (Gen 2)
will begin showing up in stores and websites soon if they aren't already listed. Functionally and aesthetically, you won't notice a difference between the two generations of Sonos One, and both will continue to be supported through regular updates.
The main changes for Gen 2 are an updated processor, Bluetooth Low Energy (BLE for setup and troubleshooting), and increased memory.
You can stereo pair a Gen 2 with Gen 1, or use them together with a Sonos home theater setup as surrounds. There aren't any functionality changes between the two, and Google Assistant will be coming to both of them when we're ready to go.