I think that Sprint will soon follow suit and get rid of unlimited data. Especially since the rise of Android devices that are so easily rooted to allow wi-fi teathering to other devices.
If the GS3 comes out anything short of a quad core, game changing beast, then I'm not going to upgrade. I just bought the GS2 (epic touch 4G as Sprint calls it) and it's running circles around my old Evo 4G.
I'm sick of these half step increments to keep us buying! Now Sprint is making the move from Wi-Max to LTE so my ET4G is already out dated. I'm hoping that there is a firmware upgrade for the radios to make the Wi-Max phones LTE compatible.