Ouch now my feelings are hurt. Nah I know what you mean.
You are right about they are not obligated to keep offering and honoring the unlimited plan. Also we are not obligated to take whatever they want us to do neither.
Sour grape / jealousy or not, when the first LTE phone came out I made the full-price non-subsidized purchase to keep what I had since 2006. I heard same thing about VZW taking us grandfathered-in folks off the hook even before VZW pulled the "unlimited" off their menu of offering.
Bottom line, VZW can do whatever they want, however the amount of folks who are GFed-in, paid in full, non-subsidized phone still makes a considerable amount of their customer base. We know, they know and everybody know these days any changes that seems "unfair" to the consumer gets amplified quickly via many different channels.
If VZW is smart enough and wanted to avoid the PR sh*tstorm, they'd make a smart decision. Class-action lawsuit is a very likely possibility if they do what you think they'll be doing. I'm sure if they can avoid paying legal fees and penalties as a direct or even indirect result of possible class-action lawsuit, they'd do a careful risk assessment.