It's a herculean effort. I heard about Opa about a year or two ago, amazed he's still at it. Kind of like Haxe. I doubt they will go anywhere, like Coffescript, because any language that simply abstracts another is just cruft and doomed to be obsoleted.
By that logic, Ruby and Python are just as doomed because they're ultimately just elaborate abstractions on top of C (or at least their reference implementations are). The implementation language and output target of a programming language are not material to the language itself. C targets a wide array of machine codes, but you'd be remiss in saying it's "just an abstraction on top of x86," and thus doomed to fail. L…
EDIT: I realized that technically my first statement is not correct: Any Turing complete language can be language can be compiled to any other Turning complete programming language. So it not an abstraction, but equivalent.