In an email to PlayStation Network users, Sony has announced the intention that by the end of the month, the PlayStation Network would be rebranded to "Sony Entertainment Network."
The rebrand is a reflection of Sony's intention to roll its gaming, music and movie services into the one centralised location, with one login for users to access everything. In other words, just like iTunes.
Sony's been working towards this for a long time now, so it comes as no real surprise that there was a rebranding involved with the PSN. After all, Qriocity was another brand that Sony is in the process of retiring.