Is there a precedent on something like this, has AT&T forced folks off of there old ones.
I have an AT&T family plan each line has unlimited LTE data. When you upgrade at subsidized pricing you're able to keep unlimited data and you also extend your contract for 2 years. The advantage to this is although AT&T has the right to change your plan even in contract, it's highly unlikely they will since you're in a contract unless you do something that violates the ToS.
With VZW if you're on unlimited and want to keep unlimited you can't sign on a 2 year agreement, you're month to month out of contract.
I feel more comfortable being in a 2 year contract with unlimited data then being on month to month.
I've been contemplating switching to VZW as I have an opportunity to get a 4 line VZW family plan for free with grandfathered UL. All 4 lines are out of contract.