I think that in the US, a national carbon policy is going to be just too tough to ever pass with the current political atmosphere. Instead, I think you'll continue to see state and city initiatives that prove carbon-neutral can be done, and the rest of the country will slowly get on board.
When the utility held an auction in 2012, it found plenty of solar power for as low as 7¢/kWh, virtually on par or better than brown electricity. The cost of renewables has been so low that the city eliminated its green energy program, which originally was offered at a slight price premium to customers who opted for it. Now, the city offers everyone green electrons at the same price – there is no premium for clean juice any longer.