That's finally been answered as well. Markus, a Sony Xperia Support team member, was found on the Sony Mobile forums a few days ago dispelling a rumor. The word had been that The Xperia S would be seeing the ICS update in June or July, but Markus says that Sony is actually aiming to release the update by "late May/early June". That means Xperia S users should be seeing the update within the next month or so.
We were surprised that the Xperia S wasn't part of the crowd-sourcing initiative of the ICS beta, so we're hoping the update doesn't come through with any bugs.