Yes, there is no cap right now, except currently in two trial markets (Nashville and Tucson), see:
»customer.comcast.com/help-and-su ··· ive-use/
But, you can't just go crazy with data usage right now, as one of those FAQs says:Q:
Does this mean you're going to stop cutting people off who exceed your allowance?A:
On May 17, 2012, we announced the suspension of our 250 GB usage allowance and that we would launch new data usage plans. We will continue to contact the very small number of excessive users about their usage, which can be indicative of security or related issues.