They already have been decreasing the width by an inch or two the past couple of years... have you noticed?
As to the original question of mixing poly in with the cotton... I don't think this would fly at all with the quilting market. Mar32428, could you have been reading an article about the cloth market in general? If so, that would make sense that fabric manufacturers would blend some poly in with the cotton, for the apparel market (T-shirts, underwear, sleepwear etc).
(Remember that quilting fabric is just a tiny segment of the fabric industry overall.)