When a new software update is released for the HomePod, users will receive an alert and will likely be directed to the Home app to install it, similar to how Apple Watch updates are installed through the Watch app. HomePod will be listed as an available HomeKit device in the Home app.
This is mostly expected, but a a relief nonetheless. I hope that automatic updates are the default here, and if possible, that the HomePod can update itself without an iOS device nearby (like it sadly is today for the Apple Watch). At the very least, software updates should be set to automatically install by default. This should not be treated like a normal tech product. More than anything else in Apple’s lineup, this should just work.