WTF is this? I'm eagerly awaiting an explanation of what you can do with X that you can't do with 2X.
It's a moot anal point. X or 2Y, using one over the other doesn't solve anything.
Far more important step for mathematicians would be to switch from base 10 to something more useful like base 8.
There are a lot of people who aren't kids, aren't mathematicians, but have to deal with maths all the time. In fact, our own field of Computer Science has a lot of math.
Now, I can't speak as a real mathematician (though I know more maths than most people), but I can definitely speak as a CS major - learning to use radians was never natural for me, and it is the basis of most of calculus. Had I learned it using Tau, I'm guessing it wouldn't have even been an issue. It wouldn't even be something I have to "learn". It just makes sense - one half of a circle is one half Tau.
The point being: for children learning the basics, the odd 2 or 1/2 here and there masks the underlying relationships. But don't take my word for it-- read the manifesto.
The whole point of learning is to learn to read things and understand them. That means looking behind 'fluff' like 2, or 1/2, and understanding the concepts.