For those who love their Chromecasts and would love to see the grouping treatment given to them, it appears that Google is starting to allow users to group Chromecasts in speaker groups on the Google Home app. However it should be pointed out that these changes only appear to affect users who are part of the Preview, suggesting that this could be some kind of feature only available in the beta.
This means that not all users will see it yet, but it should eventually make its way to everyone. Alternatively if you want you can enable the preview program in the Google Home app to check it out, but as its name implies, this is a prevent so it might not necessarily be ready for primetime just yet.
Previously, only Cast-enabled speakers and Chromecast Audio dongles could be allowed in the speaker group, but since we imagine that sometimes audio and visuals go together, being able to include your Chromecast TV is a much welcome update.