Yes, a 60% cotton and 40% polyester tank top may shrink, but it will not significantly distort the shape of the item. The amount of shrinkage can vary depending on the specific blend of cotton and polyester used. Manufacturers typically design the fabrics to minimize shrinkage, which ensures that the final product maintains its shape and size after laundering.
Cotton tends to shrink more easily than polyester, but the amount of shrinkage in a cotton-polyester blend can be considerably reduced by carefully following the care labels. In general, when caring for a cotton-polyester blend, it's recommended to use cold water and avoid using high heat settings during both wash and dry cycles.