The Sony Xperia S is due to go on sale in just under a week now and Sony Mobile is getting ready. The Sony Ericsson Update Service (SEUS) and PC Companion programs, both used to upgrade firmware for Sony (Ericsson) phones, now include the Xperia S in its phone list. The Xperia NX, the Japanese version, is also included on the list.
Given that the Xperia S has no physical buttons, you have to hold the down volume button when checking for firmware. As you can probably tell by the last screenshot, we do indeed have the Xperia S in our hands (early impressions will follow) and the below firmware was the latest available on SEUS.