I would subscribe to that, IF Unity guys bothered to settle with Xamarin and offered a modern C# compiler.
As things are, C++11 looks more appealing.
As things are, C++11 looks more appealing.
It keeps being repeated in online forums and given the current state and new direction with IL2CPP, I can only assume it is actually true.
Unity started as a Mac engine and only got big when they integrated C# into their tooling. Now that they are everywhere in the indie scene, why bother paying the guys that helped them get famous?
"Thank you Xamarin and bye"
EDIT: Provide some more context.