Officially nothing; the data sheet only listed them as “for future use.” I believe they may have gotten basic USB HID support working for special use cases with macros (eg kiosk setup with an external button to initiate a call or mute/unmute).
Newer versions of CE / RoomOS - that are not supported by the SX series hardware - have added support for audio peripherals such as USB microphones and some DSPs. There are hopes - but no confirmed plans - that Cisco will support 3rd-party capacitive touchscreens too. You may have noticed they doubled down with the latest Room Kit EQ: it has four USB A ports on it. Clearly there is more planned.
PS- Current gen hardware also supports Miracast and Apple AirPlay natively in addition to Cisco’s native wireless sharing with Cloud Proximity and the https://share.Webex.com WebRTC option. That SX-80 is two hardware generations old now.