And yet, we have orthodox Marxists who claim that religion will not go away as a powerful force in society, or can not be successfully combated, before a socialist revolution. They concern Marxism 'scripture', and are unable to take any social progress since the 19th century into account, when interpreting it.
Marx could not properly foresee the extention and nature of modern welfare state capitalism, this would have been impossible for any mortal man. Thus he believed that the level of influence of religion upon the people was mainly based on class relations, while it in fact depends on the level of secularism and welfare, as well as accessibility of information in society -- regardless of class relations.