Probably never. It's very slow to move. Yes, Java has been getting a lot of features Scala has had since (more or less) always. But it's a continuing process,

Probably never. It's very slow to move. Yes, Java has been getting a lot of features Scala has had since (more or less) always. But it's a continuing process, and not all such features are yet fully fleshed out and polished in Java. Also, Java will probably never get many of important features Scala has (or will have). It may not be some esoteric things, like higher-kinded types. But things like meta-programming/macros. Or features which may be advanced from theoretical point of view, but are actually easy from user point of view (because they lead to a simpler code), like Capture Catching.