Galaxy S2 is scheduled to get its Android 4.0 update sometime next year. However for the eager ones Samsung has released a beta ROM running on Android 4.0.1 for you to try. As expected it also runs a new version of TouchWiz and being a beta ROM there are quite a few bugs still to be ironed out. Download the ROM here and be sure to backup all your date before flashing.
Samsung releases Android 4.0.1 ROM for Galaxy S2