The story I read earlier this morning quoted someone or other as saying that customers currently in a contract won't see a change until the contract is up. If they renew, it will be at the new price.
That's wrong, because nobody with an unlimited plan has a contract any more...they are all month-to-month, as their contracts have expired.
If you had an unlimited plan and wanted to do something that forced you into a contract (subsidized phone, etc.), then you were told that you had to sign up for a new plan. For a while now, Verizon doesn't have an phone subsidies, so people with unlimited who stuck it out this long now had no incentive to switch off the plan...they would pay full price for any new device. So, Verizon is raising their rates to try to convince them to switch. It's not very nice, but it is unfortunately legal.