batting shrinks a little bit...depends on the batt and it will tell you how much on the packaging. it also depends on the amount of quilting. a heavily quilted quilt will not shrink as much as a loosely quilted one. there are plenty of batts out there that do not shrink..
some times you can get swatches (6" squares) of different battings...you could test to see ... i've been making quilts for quite a long time now and have never worried about a batt shrinking. I love wool batts they are the best! i do not pre-shrink batting, if i want a batt to not shrink i buy one that doesn't.