There's no guarantee you'll see Google talking about Assistant on the 4th, but it wouldn't be at all shocking. If the Pixelbook shows up at the event, Chrome OS is going to get some time in the spotlight -- it'd be a prime opportunity to introduce a major feature. The big question is whether or not the feature will be widely available from the start, provided it launches at the media gathering. Google no doubt wants to put Assistant in as many places as possible, but it might use early access on the Pixelbook as a selling point.