When will renewable energy replace coal and nuclear power plants?

Right now, at least in North America, nuclear and fossil-fuel-based energy is still quite inexpensive compared to solar and wind energy. However, the price of fossil fuels is continuing to rise and the price of solar and renewable energy continues to decline. Peak oil production is right around the corner, and people are increasing their demand for clean energies.

In Japan, Germany and some developing countries, renewable energies are already competitive due to a number of market forces. These same market forces are becoming increasingly relevant to consumers in North America (i.e. the high price of fossil fuels, increasing government incentives and concern for global warming, to name a few).