It seems HTC Desire S users won’t have to wait very long for the ICS update, as the ROM Update utility (RUU) featuring Android 4.0 for EU users has already hit the HTCDev.com. However, it seems the RUU was prematurely uploaded on the website, so HTC has quickly taken it down (update: The RUU is live again and can be downloaded from HTCdev.com or this direct link , it is for the WWE (World Wide English) version).
As this RUU is only meant for advanced users, so if you are not comfortable in installing it, then don’t. The initial reviews of the RUU have been decent on XDA, but there are many users who aren’t able to install it, so it is better to wait for the OTA update or an official statement from HTC (as there are rumours that Desire S might not get OTA update, but just an RUU similar to what company did with HTC Desire Gingerbread update).
There is no confirmed date for the OTA release, but considering the RUU is here, it should not ideally take long.
Installing Android update via RUU is pretty simple. All you have to do is install the device drivers if they are not already installed. Then connect the phone using USB cable to the PC and run the ROM update utility. (Make sure to take backups of everything.)
It would finish in some time and you are will on the Android 4.0 with Sense 3.6.
Few Screenshots (thanks to XDA member adisan2012):
Thanks Ketan for the tip