First firmware for Android 4.0.4 ROM for Galaxy S II has got leaked and is available for a download.
Information about the leaked ROM -
Build date: June 28
However, there is no any update regarding the changelog or improvements.
Galaxy S II will be getting official Android 4.0.4 update in coming few months.
If you want to install the leaked version then first do a backup as it is full ROM and it requires a full wipe.
Download leaked Android 4.0.4 for Galaxy S II