The Pixel 4 may launch with a "Frequent Faces" camera feature.
The new feature will essentially make it easier for you focus on the face of your subject. At least based on the information found in the data of the app's apk.
The Frequent Faces feature focuses on people you photograph most often
As the name suggests, the feature is designed to automatically focus on the face of the person you photograph most often.
According to the report about this feature, Google has engineered it to capture data of people's faces. Say you take a picture of your significant other more often than anyone else. After gathering enough data, the feature will know to focus on them.
Essentially it knows to prioritize focusing on this person, as opposed to anything else in the photo. This should come in handy when there are multiple people in your pictures. Especially when this is the scenario rather.
Face data is only stored on the device, only accessible by the camera app
Strings of data in the apk of Google Camera 7.1 point to the data being stored on the device only. Meaning it isn't being stored on servers, and that the user is basically the only one who has access to it.
What's more is that the data can also be deleted. This apparently happens automatically if you disable the Frequent Faces feature. So there's a silver lining for anyone who is a little more privacy conscious.
Should you not want face data stored on the phone, simply disable the feature within the camera app. That being said, the data will pop back up if you ever turn it back on. So, keep that in mind.
It's entirely possible that the feature won't be ready in time for the Pixel 4 launch. If Google is intending to launch it sometime in the near future however, it may very well showcase it at its product event on the 15th.
Also worth remembering is that Google tends to enjoy launching very notable new features alongside its new products. So at the very least it may announce the feature even if it isn't completely ready for user consumption.
Alongside the Pixel 4 announcement, Google is expected to announce the arrival of a new set of Pixel Buds, as well as new Nest products.