Will wide board flooring shrink?

Maybe, maybe not. If your home is in a very dry (southwest) or very wet (gulf coast) climate, acclimation prior to installation is essential to minimize movement of the flooring once installed. But remember, wood is hygroscopic (meaning it absorbs and expels moisture dependent on its environment), so all movement cannot be eliminated. Seasonal movement – shrinkage in the winter, expansion in the summer – is normal and expected anywhere north of the tropics; and the reverse anywhere south of it!