I think they are far from taking over. And for many new people they probably do more bad than good. To get really good long term profits you need to build up your reputation, this will lead to people following you and always upvoting you. This will in turn lead to people automatically voting for your post in hope to vote before the rest to maximize the curation reward.
Have a look at some of the old steemit users and you will see this pattern. And it all starts with growing your reputation by producing quality material.