Google has released v5.0 of the Google Keyboard, and this is a big one.
The UI gets lots of little changes. You can now enable borders for keys so it doesn't look like one plain surface. Google dropped the old Holo themes and the light and dark Material Design themes are the only ones available.
Google moved the emoji button inside the special character menu. There is also a new numpad button there now, which shows the numbers arranged in a traditional layout but the old row of numbers is also available. There is also a one handed mode now, which shifts the keys to either side to make it easier to reach all the keys while using the phone with one hand. Lastly, the keyboard height can also be adjusted now.
There are some new gestures as well. Like on SwiftKey, you can now swipe left from the backspace key to delete entire words. You can also swipe left or right on the space key to move the cursor in the respective direction.
The update will roll out slowly on the Play Store but you can download the APK from the link below.