Mariano Consoni has been working on both Boost.Extension and Boost.Reflection over the summer. Our current status on these two projects:
1 - Boost.Extension is mostly complete. One piece of functionality that I have not finished is the ability to automatically close shared libraries that do not currently have any loaded plugins. The main obstacles here are preserving the current Boost.Extension syntax and overcoming some platform irregularities (on Mac OS X there are two types of dynamically linked library with very different properties - bundles and dylibs).
2 - I am currently working with the code that Mariano wrote for Boost.Reflection to make it a bit more generic and do some cleanup and performance tuning.