This was inevitable, like with the previous E-Series, there were 2 versions, so it only makes sense to have 2 versions this time around. I found the information via a Korean certification website which states Sony submitted the new E460 for "radio certification" on June 16th 2011. It seems that the E460 will ship in 3 capacities, 4, 8 and 16 GB:
NWZ-E463 - 4 GB
NWZ-E464 - 8 GB
NWZ-E465 - 16 GB
Apart from capacity information, little else seems to be revealed by the filing, but it is safe to assume that the only major difference will be the addition of a WM-Port instead of a USB port and possibly different colour options.