There Sony Mobile support forum guys had gotten a little mix up with their models and the Xperia S is only getting the OS upgrade in later part of Q2 which is somewhere end June/early July. Earlier they have mistakenly announced that the roll out is coming out in the next couple of weeks around end May/early June window. Apparently this wasn’t a delay as the roll out schedule has always been end Q2 2012.
However, here’s probably a good reason to wait out a little longer. It is said that the Xperia NX which is an equivalent to the Xperia S will be getting the very latest Android 4.0.4 of Ice Cream Sandwich. This would probably iron out more bugs and has better power management. If people are made to wait, hopefully it is really worth the wait.