Here's Verizon's full statement on the matter:
"Because our network is a shared resource and we need to ensure all customers have a great mobile experience with Verizon, we are notifying a small group of customers who are out of contract on unlimited plans and use more than 200 GB a month that they must move to a Verizon Plan by February 16, 2017. If they don't choose to move onto a Verizon Plan by that date, the line will be disconnected."
A couple things to note here -- while the statement says it applies to customers who use more than 200GB a month, it's not clear whether you'd find yourself on the wrong end of a disconnect notice if you had one particularly crazy month. Rather, Verizon spokesperson Kelly Crummey indicated to Engadget that the carrier is specifically looking at users whose usage works out to "an average of more than 200GB a month" -- in other words, Verizon is targeting for people with a pattern of seriously heavy data use. The company also wouldn't confirm how many people would be affected by these changes, though Crummey did note that the customers in question "are using between 200 and 500 GB of data a month, so it is really a small fraction of [their] grandfathered unlimited plan customers."
Still, that's a very bad break for people who live in rural areas or otherwise use Verizon's mobile network as their main internet connection. It doesn't help that Verizon's detection and communication process is nearly opaque -- not to mention frustrating -- to customers on the outside looking in. The end result is a lot of confusion as to what's happening and why. Just look at Reddit, for instance -- as all of this is going down, some Verizon customers with unlimited plans have reported receiving disconnect warning notices despite having kept their data usage under the 100GB threshold. Some even appear to still be under contract (if only partially). It's not clear what's going on there, and Verizon didn't answer our question on the subject.
All told, don't expect Verizon's campaign against its own customers to end any time soon. Earlier this summer, Verizon made headlines for threatening to disconnect customers who used more than 100GB in a month. That makes this current move seem like an easing of terms, but that's not exactly the case -- as Ars Technica explains, the carrier was actually looking for people hitting closer to 500GB a month, so Verizon is clamping down on its unlimited data plan users more strictly now. If this momentum keeps up, we wouldn't be surprised if Verizon purged its UDP subscribers entirely by the end of the year.