Google may launch a new Google TV in March 2021 to replace the current mainstream Android TV. But it's not a new operating system, it's built on Android TV. Google TV will bring a new UI interface for smart TV, set-top box and other devices.
In terms of Android OS version, Android TV runs Android version 9.0, while Google TV is based on Android 10. So unless your smart TV gets an Android 10 update, you won't get Google TV.
In addition, it is worth mentioning that Sony has announced that some of its 2021 models will be equipped with Google TV, including 2021 a90j and a80j OLED TVs and 2021 z9j, x95j, x90j, x85j and x80j.