The issue I have with metered usage is that in the data world, last-mile is relatively expensive to rent, and even more so to build, which artificially limits carrier choice. You're already seeing some of the effects of this - as an example, Verizon's FiOS rollout, they've stopped the rollout in many locations because they can't pay for the physical infrastructure, so many customers are locked in to their current carrier (even when they want FiOS). It's not like wireless where you can simply switch carriers so data pricing stays reasonably honest.
With that being said, you have less incentive for data caps/metered pricing following the mobile model where pricing is kept reasonable by carrier choice/number portability. As backbone increases, there's no reason for Comcast/TW Cable/RCN/etc. to increase the data tiers/lower cost per Mbps, so I believe you'd see costs creep upwards as data consumption grows.