If you only use official Portal releases, there is no need to worry about Portlet Container. Each Portal release will integrate the appropriate version of Portlet Container, which might or not be different from the one used in a previous Portal release.
Portlet Container is NOT a supported product at this time, only Portal is.
Portlet Container 2.0 will continue to evolve as we see fit. The fact that it has been extracted to a completely separate modules theoretically allows people to replace the version of Portlet Container used by a given version of Portal (post 2.7). However, this does not mean that such a replacement will work with any given version of Portal. For this reason, the only versions that will be supported are the ones that the Portal team will integrate in an official Portal release.
Portal 2.6.4 is NOT compliant with JSR-286 and will never be. Portal will provide support for JSR-286 starting with Portal 2.7. It is NOT possible to replace the portlet container used by Portal 2.6.4 with a JSR-286 compliant portlet container without significant efforts (comparable to implementing Portal 2.7, so you might as well wait for us to do the work ^_^).
RichFaces is a separate project. We plan on providing better integration with it.
Thank you Chris!