I was grandfathered into the unlimited plan for $29.99. Yesterday, I had a chance to talk to a VZW representative about a replacement phone for my son, who had a basic, texting phone which conked just after the original warranty had expired. (He's on my plan w/ four phone of which only one, mine, is a smartphone.) They suggested an incentive of upgrading him to a smartphone for a two-year upgrade price and giving him, individually, 2GB of data for $29.99. I asked several times if my unlimited plan wouldn't be touched, and was told that I could keep it as is. This last part I still have a hard time believing.
As an alternative, they suggested a shared plan with 2GB for the whooping $200, with each further 2GB increment for extra $10. Obviously, the latter would be crazy to accept, but, overall I found, the price difference staggering.