I haven't noticed that batting is getting thinner, but it's possible as so many businesses are cutting corners where they can to keep costs down and stay in business.
There are batting companies like Quilters Dream that make many different kinds of batting..., poly, poly blends, cottons, silk, bamboo, wool. Their Dream Cotton comes in several lofts --different thicknesses -- and is wonderful stuff. I prefer the Select loft, but they have 2 more that are each thicker than Select.
http://www.quiltersdreambatting.com/default.htm
Jan in VA