I've been reading up on it and apparently it's not Sony's fault - it's Google's as they've given Samsung special early access to ICS, playing favourites with your "partners" doesn't seem like a good way forward IMO.
Still, I can't imagine ICS for the Xperia S is very far off - ICS is also coming to both the Xperia Arc and the Xperia Arc S (amongst other models*)in the very near future (March/April).
The Xperia S is due to market at least a fortnight sooner than the HTC One X, which could explain the difference between Gingerbread & ICS at launch.
*see here:
http://blogs.sonymobile.com/products/20 ... pril-2012/