According to screenshots, your iPhone will show you a notification like the following: "Disconnecting Nearby WiFi Until Tomorrow" with an explanation about how the current network and others nearby will be disconnected until the following day. It also states that "WiFi will continue to be available for AirDrop, Personal Hotspot, and location accuracy." You'll see Bluetooth in the notification if you tap that button. This third iOS 11.2 beta comes a week after the second beta, which includes Apple Pay Cash via the Messages app and a few days after Apple released iOS 11.1.1, which fixed an annoying autocorrect bug.