The Software Engineering Radio podcast recently had Michael Stonebraker as a guest to discuss his take on the future of relational databases.
Dr. Stonebraker is a professor at MIT, and is currently part of the VoltDB team, which is a distributed ACID/SQL database management system.
In the interview, he talks about how he sees the current relational database world breaking into three directions: One to NoSQL, the Data Warehousing segment moving toward columnstore storage, and the remaining segment moving to in-memory tables, to get away from locking and other overhead associated with current OLTP processing. He also discusses the value of ACID compliance, which is discarded by most NoSQL systems.
There’s also this post with an accompanying slideshow and a video with a more in depth discussion of the same topics.

July 17, 2015:
Added some additional links:
Urban Myths About SQL – Slides

2014 Turing Award speech video

One Size Fits All – An Idea Whose Time Has Come And Gone (Video)