Nobody wants redundant home audio equipment. Speakers take up space, but in the age of near-ubiquitous smart speakers, a lot of them just sit around in our homes doing a whole lot of nothing. Damn lazy speakers. With an upcoming update, your HomePod mini will finally be able to start pulling its weight around the house. Maybe it'll even get a job.
Provided you have an Apple TV 4K, you'll be able to set your HomePod minis (HomePods mini?) up as your television's speakers. It's not clear how many HomePods will be supported for output simultaneously, but at least two, obviously.