We have mostly finalized the list of bugs and features that we will finish before the new stable branch of libguestfs (1.6) is created. You can view the list of 1.6 bugs and features here. Although I can’t promise exact dates, we’re hoping to have this out in November.
libguestfs is also due to be rebased for RHEL 6.1, and that will (probably) be based on upstream version 1.6. The new version is much faster (about 4x or 5x faster) than the version we are shipping in RHEL 6.0, and has a very large number of new features, but is backwards compatible with RHEL 6.0 so no code or script changes will be required.