Well, i don't think that we can say for now that this is already a career. It's something that the market is feeling that is needed and so it appeared like this, such as professionals that are talking and developing actions and plans to get to one better ranking on the search websites.
I think that for now the person that is specialized on it is getting a differentiation on the market, but in other hand, as the things on technology change all the time, we can't say that is really safe.
But for now i think is a good field to specialize yourself