Hi everyone, dear Matt!
Matt Walker has posted an extensive review of ROOT and what he would hope the future of ROOT to be. Because I think many of his comments are good ones, and because I have heard some of them from several people in the past, I decided to give the answer to an audience that's little bit wider, in a dedicated post.
This is a companion discussion topic for the original entry at https://root.cern/blog/root6-and-backward-compatibility/