First up, the HomePod is getting better with the addition of stereo pairs and multi-room audio. The stereo pairs feature will let you use two HomePod speakers as a stereo pair, while multi-room audio utilizes AirPlay 2 to stream audio to multiple AirPlay 2 devices (not just the HomePod) throughout your home with the audio in sync.
AirPlay 2 is a major update for Apple's wireless audio tech. It adds a larger buffer so any small network issues don't interrupt your music as well as a tighter clock sync to enable the aforementioned multi-room audio.
Also included with iOS 11.4 is Messages in iCloud, which syncs your iMessages between your iOS and Mac devices so that you'll always have up-to-date texts.
Rounding out Apple's announcement is the news that the HomePod will launch in Canada, France, and Germany on June 18th.