I think making 'Ellipsis' a reserved word is too much.  The analogy with non-reserved words like `int`, `str`, `map`, `print`, and so on, illustrate this, I think.  I.e. redefining those is likely to cause bad things to happen, but we're consenting adults, and in the end they are just names.

However, I think improving the repr() of the Ellipsis object itself to remind users of the connection with its special literal `...` is a great idea.