According to the Sony Ericsson Developer Blog the new line of 2011 Xperia smartphones will allow “advanced developers” to unlock the boot loader legally. This feature will only be available on certain devices that are without specific restrictions. For example a device that is SIM locked to a carrier will not fall into this category. Sony Ericsson wants to make sure everyone is aware this procedure may still void the warranty and to check the warranty statement for details.
Sony Ericsson is providing their own online web portal where the handset owner can obtain a key to unlock the boot loader. They describe this method as entering the IMEI into their web service and using the key in Fastboot where the actual unlock procedure takes place. There will be more detailed instructions once the service is online. Simply connect your device to the Fastboot tool in the Android SDK to find out if your device is eligible. If it connects, your device is compatible with this new service.
The 2011 lineup of Xperia devices that may be compatible are:
I am curious to see if this is a trend that will continue and how the community responds.
Source: Sony Ericsson Developer Blog