I think having multiple options is always a bad idea for a language. It complicates the syntax and make people ask why not make parenthesis optional for loop statements as well? Then they perceive this as imperfect design - consciously or not. To me personally, this looks like a patch put in place just to entertain the Ruby crowd and is not along the lines of the solid unambiguous syntax that you're striving for!

And you'll break backwards compatibility with every app written prior.