Sony Mobile has officially announced on their blog they have started rolling out Android 4.0 (Ice Cream Sandwich) update for Xperia P as they promised. This update would bring new features including new lock screen with improved functionality, Resizable widgets, Recent Apps button, WALKMAN, Album and Movies apps. Sony started rolling out ICS update for Xperia S in June.
Xperia P users will get a notification regarding the update. It would be available Over the Air (OTA) (depending on the regions and carriers) and via PC Companion on Windows/ Bridge for Mac. This update would be rolled out over the next few weeks and the availability might vary across different carriers and countries.
Sony Mobile has also announced that the Android 4.0 update for other 2012 Xperia phones such as Xperia U, Xperia sola and Xperia go would follow.
[Update: Sony Mobile has announced that the Xperia P would have Extended Standby Mode feature along with the ICS update. This would increase the standby duration by up to four times by shutting down background Apps and Sync. You can enable it from Settings – Power Management – Activate Extended Standby Mode]