His opinon of relational DBs is that
their dominance is due less to their role in data management than their role in integration
This makes sense, but I think they also have offered the benefit of providing a fairly powerful, standard way of modelling and querying data. Over the lifetime of this technology this has fought off some powerful challengers, notably object-oriented data modelling. (Although perhaps this battle was only won by becoming more like the "loser"). The latest challenger is semantic data modelling (RDF, SPARQL, etc). Perhaps the world is ready to make this transition - although I'm not rushing to sell my Oracle stock.
He also makes a good point that the focus of integration is shifting from the DB to the Web. Hard to argue with this... the clouds are moving in!