OSGi is powerful stuff by itself; I don't know that there's anything more powerful out there. But you can use it on different levels: bundles, services, embedded container, etc. I've used the Apache Felix implementation, and occasionally Apache Karaf as container on top of that.
I don't know RCP, but Java 9 is going to have a module system that replicates some of what OSGi does, and will reportedly have some degree of compatibility with it. (Of course, that was said about Java 7 and Java 8 before, so we'll have to wait and see what actually materializes.)