Google has released an update to Google WiFi that, along with the latest firmware for your WiFi or OnHub devices, will allow you to enable IPv6 to your ISP. For those who are not familiar with IPv6, it is a more advanced version of IPv4 (which you are likely using now) that uses 128-bit addressing of devices. The theory is you can get more devices on the Internet because there is significantly more IP addresses available with v6. The lack of IPv6 has been a contention point for many who use Google WiFi or OnHub as it is more secure and is somewhat of a checkbox requirement for a contemporary network device.
The update to bring IPv6 is a combination of firmware for the physical device itself, which is build 9460.40, and the updated app which is in the Play Store.