Well, that was...unexpected. It seems with all the Pixel 4 leaks, Google has just outright confirmed that the Pixel 4 exists and the external look.
Just yesterday, we reported about the leaked Pixel 4 renders that were going around. Google's photo confirms that those renders were actually correct. The Pixel 4 will indeed change from a single rear facing camera to a multi-camera setup. Entire enclosure will be in a square enclosure similar to the rumored camera bump of the new iPhones.
That said, the picture that Google tweeted out doesn't show the front of the device so we don't know exactly what it will look like. However, we can surmise that since the rear mounted fingerprint sensor is missing, Google is either using a side button as the sensor or an in-display fingerprint sensor. With the proliferation of in-display fingerprint readers as of late from the likes of Samsung and OnePlus, I'd be fairly certain of the latter.
Internally, the Pixel 4 will likely have the requisite high-end specs: Snapdragon 855 processor, 6 to 8GB of RAM and at least 64GB of storage. Pixels usually don't offer storage expansion via microSD. Ars Technica reports that Google's Project Soli may be supported on the Pixel 4. Project Soli is basically a tiny chip that uses radar to detect hand motions above the device. It will be interesting to see if those air gestures will actually be useful unlike Samsung's attempt with Airview on the Galaxy S4.
Regardless, Google is clearly trying to go next level with the camera and teasing a lot more for the future.