I didn't downvote, but I don't think the problem has anything to do with specific language features. It's purely a political issue: you have to get at least two or three main vendors to adopt the new language at the same time, and none of them must perceive it as a threat to its own agenda. For that to happen, all of them must release compatible implementations that put everyone on an equal level at the exact same time, which is really hard to accomplish. It was very hard even to get javascript where it is now (remember the browser wars and all the incompatible extensions it spawned... ?), starting again from scratch with any new language would be extremely difficult, regardless of how "nice" the actual language is.