Ellipsis False None NotImplemented Trueare the builtin singleton data constants, so I'm +1 on those.
I'll go along with True and False, since I expect that these will be frequently used (though still not as frequently as None).
Ellipsis is very rarely used (only by numeric code implementing multi-dimensional arrays), NotImplemented is used somewhat more but still pretty esoteric. So I'm -1 on those.
Otherwise, you might as well start making all built-in functions keywords -- that would probably buy you more, too. E.g. if range were a keyword, the compiler could implement "for i in range(n)" without materializing the whole list at once. But I'm not proposing that; I think there's a better way to get the same effect without making everything a keyword.
I just think that None is important enough to become a keyword.
--Guido van Rossum (home page: http://www.python.org/~guido/)