Samsung has announced that both the Galaxy S and the Galaxy Tab can handle the upgrade to Android 4.0 when looking purely at speed of the device.
However the upgrade will not arrive on these devices simply because certain hardware features will not function.
The quantity of RAM and ROM in this is a big factor.
Some of the Touhwizz functions Samsung uses will not work when combined with Android 4.0 and one of these devices.
Based on that Samsung had decided to exclude the Galaxy S and the Galaxy Tab from the upcoming updates.
For the following devices it is a FACT they will receive their updates:
GALAXY S II
GALAXY S II LTE
GALAXY Tab 10.1
GALAXY Tab 8.9
GALAXY Tab 7.7
GALAXY Tab 7.0