Change takes time! This is a great example, as he has specific instances of evolving syntax to describe the same thing, semantically.
The big problem, of course, is that code hangs around. Can you evolve your syntax as people get used to it? Not only are you adding work to your parser, but people who use your language also have to deal with the multiple iterations of the syntax that linger in various codebases. This is one reason I detest dealing with Perl codebases.
Anyhow, as an exercise of evolving syntax while keeping the underlying semantics, I find Reason [1], a new syntactic layer over OCaml, particularly interesting.