New version of dcl is coming: dcl6. This is an experimental version written from the ground up specifically to take advantage of new ES6 language features: new class keyword, new super mechanism. The implementation uses symbols to keep innards truly private.
The principal coding has been finished several months ago, and the new library was under extensive real-world testing. Missing features: debug module is unfinished, and the documentation is in early stages. So right now it is only for brave developers, who feel comfortable reading tests and the code to understand the changed API, and who are not afraid to encounter possible bugs.
Logically, it is based on dcl 2.x branch and supports all advanced ES5 features as well. Of course, it supports chaining and AOP advices we all come to love. It even provides the same set of advices, mixins, and utilities. As before, it has no external dependencies, and minimal in size.