First the disclaimer: I am not a solar buff. Wind is much closer to commercialization, but even wind is still subsidy dependent and solar has considerably farther to go. My preferred clean energy strategy for the immediate future would be to build lots of nuclear power plants.
However, the costs of solar continue to decline and there is a great deal of research underway. The Solar Energy Industries Association reports that photovoltaic installations have been increasing by more than 25% annually over the past decade and more than 35% annually over the last five years. That's a global figure.
Yes, a lot of that is driven by government subsidies, but solar is also beginning to expand into legitimate markets for off-grid applications and a wide variety of low-intensity uses. This is only marginally helpful in terms of the aggregate national power supply, but it is interesting from an industrial policy standpoint because it begins to support an expanding industrial base, which will increase economies of scale and innovation.
Meanwhile, the costs of conventional power continue to increase. Will the trend lines cross? I don't know, but I have moved from being a wind/solar skeptic to being bullish on wind and agnostic on solar. Wind and solar combined currently produce less than 1% of our electricity but a number of states -- not the feds -- are beginning to set much more aggressive targets.
Adding it all up, we will be dependent on coal, natural gas, and nuclear for decades to come, but I would not be at all surprised to wind, and possibly solar, build out to a 10-20% share over the next 20 years. It could be higher if subsidies are increased and/or serious carbon taxes are enacted. In the near term I would expect wind to build out much more rapidly, but in my admittedly layman's opinion, the potential for technological breakthroughs and really significant reductions in manufacturing costs is probably higher with solar.