Yes, I hope they end up in some future version of Dart.
In the meantime, enum_class is actually exactly designed to match Java functionality. On my project we keep Java and Dart equivalents for the same enum, and use them in RPCs. So we want the Dart enums to be able to carry code / implement interfaces, like the Java ones.
A quick look at the big picture / master plan:
+ built_collection.dart: released and stable, immutable collections with the builder pattern
+ enum_class.dart: just released, Java-like enums
+ built_value.dart: coming soon, codegen to help build nice immutable value types
+ built_json.dart: coming a bit later :) ... JSON serialization for all of the above: collections, enums, values
+ Built JSON for Java: Java equivalent serialization so you can use all of the above for RPCs; on the Java side you'll use @AutoValue
Cheers
Morgan