AT&T did make that announcement, with a similar rationale to Verizon's:
Wheeler should go after AT&T as well. What both companies should have said was that anyone using over X GB of data per month would be throttled. Period. Set the bar, and then it doesn't matter what plan a customer is on; if the limit is exceeded, the throttling begins (except obviously for someone who has the resources to buy boatloads of data each month). I think Wheeler's concern in this case is that Verizon (and AT&T) specifically targeted users who originally purchased an unlimited data plan. That seems unfair. The expectation for "unlimited" is not "throttled".
Perhaps the problem the telecoms have is that all of their other plans do have specific caps, whereas the unlimited plans don't. But then, as someone else said, they should just abandon the term "unlimited". Problem solved.