When you're trying to change things, it's best to appeal to the early adopters and to do give them a real reason to switch. Making it look the same and appealing to the same "user base" won't work, because then they might find little reason to switch in the first place.
I learned LISP and Python before Java and C#. The latter two are just as useful nevertheless.
The world's experience outside of HN makes me think Dart will not be at all inhibited by its Java like syntax. If it doesn't catch on, it will be for other reasons.
