They announced the same thing on the 2014 post.

They do have some kind of mono compiler update in alpha according to their roadmap [1], not for the runtime.

I wouldn't hold my breath, that's all.

[1] https://unity3d.com/unity/roadmap

But now there is an open source and cross platform compiler/runtime that they can use, dot net core. It should be much easier to incorporate that into unity.