Sony has updated its Xperia Keyboard to build number 6.4.A.1.24, which introduces a number of new features. This includes a larger spacebar to make it easier when typing and new language support (Armenian, Azerbaijani, Belarusian, Georgian and Tatar). Other features include a Phonepad layout on the Xperia Z2 and the addition of a numeric row to input numbers on tablets. The update is currently live through the Google Play Store.
If your phone is rooted, you can download the app here and move it to system/app. You will then need to set the correct permissions (RW-, R–, R–) and reboot your handset once completed. The keyboard has also been ported to run on devices with Android 4.1 Jelly Bean and above, head over to XDA to give this a try.
Thanks Ben, Niclas, Rimas!