[boost] [Math] Statistical Distributions parent distribution class

In the Statistical Distributions section of Boost.Math there is a future directions link that talks about an "any_distribution" class. Is this planned for a future release? Is anyone working on this? I came across a need for this when writing a lambda to find the pdf of a certain value of a random variable. It would be helpful for iterating over a vector of random variables whose distributions are not the same.