I'll admit this isn't from the most credible source on the internet but NeoGAF user, Psykotik, says they received an e-mail from Sony that notified of this change.
I haven't gotten this e-mail yet but I think it's very likely this is true since Kaz Hirai was recently appointed CEO and President of Sony. With that, he's mentioned that he wanted to make some changes to get Sony as a whole back on its feet. Losing the PlayStation moniker most likely also means that they'll be expanding this service to platforms that aren't necessarily PlayStation.
On February 8, 2012, your “PlayStation®Network account” will be renamed a “Sony Entertainment Network account” or a “SEN account” in conjunction with Sony Computer Entertainment’s PlayStation®3 system software and PlayStation®Vita system software updates. (Note, this change will not be applied to the PSP® (PlayStation®Portable) system at this time.)
This transition is based on Sony’s goal to enhance its unique digital entertainment offering. As a series of these activities Sony started last September, PlayStation®Network will be aligned with “Sony Entertainment Network.” This helps us get closer to our goal of establishing a global comprehensive network platform of services across games, movies, music and more, all accessible from one convenient account.
Thank you for your continued loyalty and support during this transition.
The Sony Entertainment Network Team