The additional cost for the hybrid isn't so much in the engine as it is in the batteries. I've read about some pretty good breakthroughs in battery technology. Once some of that gets into production, and once production demand is high enough to reach economies of scale, then I think you'll see a lot of the price difference evaporate.
The problem in reaching economies of scale though is that you need a catalyst to get you there. Most people if you ask them "Would you drive a hybrid/electric car if it had the same performance and cost as a normal car?" would say yes, but the price difference is a big barrier to entry. The catalyst can come from either consumer demand, which high gas prices induces, or government mandate.
I'm generally a free-marketeer, but this is one of those cases where I don't think the common good is fully served by the supply and demand model. For consumer demand to really increase long enough for the major auto companies to be willing to invest in the production changes necessary to reach those economies of scale, we'd need high gas prices (north of $3 at least) for a protracted period (3-5 years).
Now that could, and imo likely will happen in the future, but the effects of that high gas cost on the economy is what causes me to support government intervention in this case.
US consumer spending is about $8.7 trillion per year, which is about $287 billion per month. When gas was at $1.50/gallon, it was estimated that for each 1 cent raise in gas prices, approximately $1 billion was taken out of non-energy consumer spending per month. The relationship falls as gas prices rise over $2/gallon as consumers still spend, but use more borrowed money to do it.
A protracted period of gas prices at the $3 or higher range would not only crush non-energy consumer spending, but the ripple effect could easily push us into a protracted recession or even a depression.
So I don't think we can just sit around and wait for the consumers to fully embrace the hybrid/electric car and manufacturers to put the capital into it. I think we need to government to force the manufacturers hands a bit so that when this protracted increase of gas prices occurs, consumers can easily make the shift to more fuel efficient vehicles.