Android Version: 4.3
Stock Xperia™ Keyboard: 6.2.A.0.30.4
Upgraded Xperia™ Keyboard: 6.4.A.1.52
Root: Yes (via Towel Root)
Check on XDA Developer Recognized Themer @Ben Ling and his post Latest Xperia™ Keyboard 6.4.A.1.52
Download the textinput-tng-emoji.apk (Xperia Keyboard 6.4.A.1.52) and rename it to textinput-tng.apk
Then manually (via a file manager) copy the new textinput-tng.apk to /system/app and overwrite the existing textinput-tng.apk.
Check the permission is still -rw-r--r-- 
Now reboot the phone.
When the phone reboots, it may not show the updated keyboard and shows the Chinese/Voice keyboard instead.
If there is no errors saying: "Unfortunately, Xperia keyboard has stopped" you're still OK.
Just go into settings -> Language & Input menu and deactivate any other keyboard methods and then tap on "Default" and set up your "Xperia™ Keyboard"
Now you should have your new Xperia™ 6.4.A.1.52 Keyboard.
To install a better set of black and white Emoji than what is available in Xperia™ 6.4.A.1.52 Keyboard look at the following:
ALL XPERIA | Xperia Keyboard 6.4.A.0.6 | With & Without Emoji support
Download the JB 4.2 & 4.3 emoji zip file.
Now extract the approx ~2MB AndroidEmoji.ttf file from the zip file and copy/replace /system/fonts/AndroidEmoji.ttf
A reboot and you should have a new keyboard and better black and white Emoji i.e. people Emoji and not silly Android antenna smiley Emoji.
Android 4.3 does not support coloured Emoji on a default Xperia Keyboard outside of the likes of WhatsApp.