Nest Wifi units will work with the older Google Wifi units. Nest Wifi Pro only works with other Nest Wifi Pro units.
Make sure that you purchase the new Wifi point from the same country where you'll be using them / same country as your existing Wifi points. Since wireless regulations vary by country, you might experience compatibility issues if you try to use them in a different country, and Google will be unable to offer support. If you're setting up a mesh network, it's strongly recommended that you purchase all of your Wifi devices in the same country to avoid compatibility issues.
