http://open-std.org/JTC1/SC22/WG21/docs/papers/2013/n3526.html

Bristol 2013: Stroustrup thought that the proposal is too aggressive and removes structure, and thought that the existing limitations are deliberate. Stroustrup and Sutton also pointed out that there are existing matrix types that deduce the shape of the matrix from the initializers, and this change would break such existing code. No recommendation to move forward, considered NAD.