Samsung promised a Froyo update for the Galaxy S devices when they were released, but several months later there was still no update and then the devices finally received the update in the Spring of 2011. Thus, it should really come as no surprise that the Galaxy S and Galaxy Tab are currently not likely to get an Ice Cream Sandwich update.
Reportedly, Samsung states that the Galaxy S devices lack sufficient RAM and ROM to run ICS with TouchWIZ and other Samsung optimized software. The Samsung Galaxy S sport a 1 GHz Hummingbird processor and has the same internals as the Nexus S that is now getting the ICS update. Here we can see the problem with buying Android devices with "skins" where Samsung states they have to update the existing Samsung Galaxy S variants with the customized TouchWIZ interface rather than pure ICS.
Update policies like this confirm that my expensive purchase of the Galaxy Nexus with pure Ice Cream Sandwich was the right move and I doubt I will ever buy another Android device with customized user interface.