I’ve heard it argued that they’re not necessary now, which is only partially true, I think. As semantic search becomes more the norm, then I expect keywords to become less important. They are certainly a lot less important in conversational search, as demonstrated by Danny Sullivan.
The big question is, When will Google take the semantic aspects of conversational search and apply them to organic text-based search? I figure it could happen within the next five years – probably sooner.
Of course, that won’t immediately kill the need for keywords. I suspect that keywords will always be a part of search but in a more diminished way as search becomes increasingly more sophisticated. Personalization was one step in that direction. Google+ is another step. Conversational search is a big leap.
Keywords are still necessary because they are a good way for search optimizers, searchers, and the search engines to communicate on common ground. What Google is increasingly trying to do is make search more like natural conversations.
So the big question on the table is, How long will it be before Google succeeds at making search entirely conversational, completely semantic? You want to take a stab at that? Will it be within the next five years?