Today, Samsung updated the Galaxy Tab 10.1 WIFI to Android 4.0.4 in USA. Samsung will update the most of their tablets to Android 4.0. If you have the Galaxy Tab 10.1 WIFI and you live in the USA you will be able to update your tablet.
You can use Samsung KIES or OTA for this update. Make sure the WIFI is on for OTA updating.
If you want to flash your tablet is this also possible. Go to www.SamFirmware.com and download.
Please flash only your own country.
Some details about this firmware:
This firmware is specially for USA (Android 4.0.4)
Build date August
Changelist: 818980
PDA: P7510UELPL
CSC: p7510XABLPL