Is the Relational Database Doomed?

Tony Bain wrote "Recently, a lot of new non-relational databases have cropped up both inside and outside the cloud. One key message this sends is, "if you want vast, on-demand scalability, you need a non-relational database". If that is true, then is this a sign that the once mighty relational database finally has a chink in its armor? Is this a sign that relational databases have had their day and will decline over time?"