I saw this article on Macrumors:
Verizon Planning to End Grandfathered Unlimited Data Plans With LTE Switch - Mac Rumors
It says basically when you upgrade to an LTE device that Verizon will force you onto one of it's family tiered plans. Now I don't know if you have an LTE device already if that gives you a pass on this, but I'm guessing not. Looks like I will be going to Sprint as soon as possible.