While it will take some time for the Samsung to roll out ICS (Android 4.0) theme for the Galaxy Tab 8.9, an xda user has already developed a theme that brings ICS look and feel. This theme is compatible with Wi-fi only version of the 8.9 Tab (P7310).
Before you flash it, your tablet must be running the Overcome ROM for 8.9 tab. Here are the instructions on how to install it:
* Download theme. link
* Save on internal SD card.
* Boot into Recovery.
* Wipe Cache
* Wipe Dalvik Cache
* Flash Zip
* Reboot