Indeed - but wind gets cheaper every year, while gas and coal do not.  That's why it's growing so fast already and will keep on going.  Within 5 years the economics for wind will be accepted fact.  In ten years, wind will have at least 5% of the US market, and will keep growing like crazy.  Right now, installed capacity is doubling every two years!
Wind is limited both by available sites and by the fact that it destabilizes the grid if there's too much of it because it's so unpredictable and uncontrollable. I think the utility people believe they can't take more than about 10% of the total in wind power. Note that it's current economics will tend to worsen in a post-peak world since the steel for the turbines won't be subsidized by being mined and smelted with cheap energy.