That percentage may well represent nameplate capacity at full load, not actual power delivered on average.
Iowa, Kansas, and Okla are up of 30% windpower. Texas is 18%
The prices will continue to fall and renewables will be implemented elsewhere.
The price of offshore wind has fallen so the north and mid atlantic states will be installing windmills there over the next 10 years.
The article points out that 29 states have renewable electricity standards. Iowa's first renewable standard was in 1984. In Texas it was 1999. New York cranked theirs up to 50% in 2015 based on installing the offshore turbines
Same with the car batteries. They were over $1000/kwh in 2010 and are now $200/kwh and will continue to fall.