That's right: The spec will never be revised, not because it already defines the ideal programming language (is that really your argument?), but because the effort and expense is so great.
Maybe somewhere in between. The imperfections are so small that even a modest effort would never get undertaken. Something folks need to realize is that Lisp truly is a metalanguage: I think both Graham and Norvig knocked off quick and dirty OOP hacks when that (decent) fad came along. So it is hard to imagine what innovation might come along that would force us to get the Lisp hood up.
