Wind turbines are already at 5-7 cents per kWH or grid parity in the best sites in the US and the majority of installations in 2016 are expected to be at grid parity. Presently, newly built wind energy is cheaper than newly built generation of any type except natural gas. Costs have dropped 14% for every doubling of installed capacity over the past 30 years. Projections are for another 20-30% drop over the next 20 years before levelling off.
What do the best studies say?
Recent studies by the Lawrence Berkeley National Laboratory (LBNL) and a joint Queens University / Michigan Technical University show that both solar and wind are at or better than grid parity in the best sites, with wind having seen the most significant movement to a cost of 3 – 6 cents per kwh, below that of natural gas. . , , 
This is due dominantly to massive and relatively uncelebrated increases in wind capacity factors in all wind resource categories combined with significant turbine cost reductions in the past two years.
To translate, while critics claim 20%-30% capacity factors, real capacity factors are in the 35%-47% range.
Research published [in November 2011] by Bloomberg New Energy Finance (BNEF) said that the best wind farms in the world already produce power as economically as coal, gas and nuclear generators, and predicts a 12 per cent drop in price over the next five years.
As manufacturing, operations and maintenance costs have dropped, the cost of energy before any subsidies or support mechanisms produced from onshore wind turbines has fallen by 14 per cent for every doubling of installed capacity between 1984 and 2011, BNEF said.
This represents a real-term decrease from €200 per megawatt hour (MWh) to €52/MWh, only €6/MWh more than the average cost of a combined-cycle gas turbine. BNEF said that, if the cost of gas includes the cost or carbon emitted, wind would already be at grid parity. 
When the California Energy Commission published “Comparative Costs Of California Central Station Electricity Generation” in 2009 , the full-lifecycle analysis of costs including regulatory and zoning costs, insurance costs, construction costs, financing costs, maintenance costs and fuel costs over 20 years found that wind energy was very competitive with most forms of energy without any specific subsidies.
This comparative advantage is projected to increase by 2018 as wind’s advantages of zero fuel run costs contrast with increasing prices and more limited siting options for most other forms of energy.
Subsidies and regulation favouring wind energy are merely leveling the playing field sufficiently that its inherent efficiencies become viable in a conservative industry with strong systemic biases toward traditional energy sources.
The International Energy Agency, the most trusted source in energy, agrees. Their 2012 World Energy Outlook shows that new build of wind energy generation is cheaper than new built coal, nuclear and hydro generation, in fact cheaper than anything except new natural gas generation. 
What’s really happening?
This is not just theoretical, by the way. Wind generation proposals won 80% of the contracts at a December 2011 Brazilian power auction, beating gas and hydro proposals based on an average cost of power of 5.5 cents per kwh for almost a gigawatt of generating capacity across 39 projects. 
What other factors are in play?
Another key factor is that in many jurisdictions, markets for energy favour energy sources with low marginal costs such as wind, which is close to a zero marginal cost when the wind is blowing. This depresses the effective rate that everyone is paid. This is known as the merit order effect. In one study, consumers in the midwestern USA might see a $63-$200 annual reduction in their electricity bills due to market forces.
In Australia, this is saving consumer money as well, $7 per year with very little penetration of wind energy.
What does it look like in the longer term?
The IEA, NREL and LBNL collaborated on a study to project long term cost of wind energy and published their report in May 2012. Median projections range from 20-30% further reduction by 2030. This puts wind in the 4-5 cents per kWh range. 
Wind is a very effective part of our energy mix today and will only become more effective compared to alternatives.