Good riddance to Unity. That was essentially an unnecessary fork of Gnome with polarizing opinions (on top of the polarizing opinions of Gnome). I think shifting back to Gnome 3 is the right decision in the long run (especially since Debian uses Gnome 3). That said there are features of Unity I like, but not many.
Where do you see that Mir is going away? Not seeing it in the article. That said, I again agree that Mir is unnecessary when we have Wayland.
Ubuntu phone was, in my opinion, as DOA as Firefox OS and Tizen, and Windows Phone.
Tablets...i have very strong opinions about tablets that you can poke me about later.
Microsoft can't even get convergence right with Windows 10, and they have the money to do it, but then again this is Microsoft we are talking about. Android/Chrome OS are going to be closest we get (and it appears to largely be successful in Samsung's Galaxy S8, app support notwithstanding).