I saw this over at Uberphones, and it looked pretty.

The leaked picture you see is actually rumored to be Sony Ericsson's latest GSM handset and has been given the number W999. This slider cellphone comes with a keyboard that is pretty similar to the M600 smartphone. There is no word on the W999's (if it is even real in the first place) operating system, but we do know that HSDPA connectivity is supported.

Given the prominent 'W' on the front (and, as Uberphones point out the W in the model number) it's likely this is also a Walkman phone. Uberphones have more.