Daniel Eran Dilger, AppleInsider:

Apple did introduce Siri Intents for HomePod, enabling App Extensions to take over the handling of specific requests, such as third-party messaging or list-management apps. You can expect to see an expansion of these Siri Extents for HomePod this year. HomePod shipped with a notable lack of support for features Siri can already handle, including Calendar tasks.

A nit: Calendar was promoted to HomePod in the latest release. Not perfect, but definitely there.

The fact that HomePod packs a speedy processor and is unconstrained by battery limits means that HomePod could eventually serve as a smart home computer in the background. Both HomePods and Apple TVs could be orchestrated to handle background tasks distributed across your home network.

And:

Additionally, the fact that HomePod has some onboard storage and a fast processor means that Apple could eventually delegate it tasks that are otherwise wasting battery on your mobile device. Imagine if, rather than Photos doing background imaging processing on your phone for face recognition and album creation, all your devices simply synced your photos to iCloud and your HomePod took advantage of its idle time to process your images in the background, synching them back to iCloud and back down to your devices.

Offloading battery-sucking tasks to the always powered HomePod is an interesting idea.

Daniel’s article is worth reading, some thoughtful speculation.