Chromecast firmware has already been upgraded. I'm waiting for a code or open sign up period, so I can activate in app. Link controller to WiFi and pay for pro subscription.
@MiloH79 We don't know when Google will open it up so that you can purchase a Pro subscription separately from the controller + Chromecast bundle. Right now that bundle is the only way to get access to Stadia.
@codesplice Thanks for the clarification! Very helpful. Of course it's unfortunate for those of us who already kitted out our viewing setups with Chromecast Ultras before Stadia was announced; wish Google would provide an option for those of us who already use its ecosystem.