Linus Torvalds describes the just-released Linux 2.6.39-rc2 kernel as being an "uncommonly calm" release and points that may lead it to being a "simple release" if nothing changes.
There simply aren't too many regression fixes going into the Linux 2.6.39 kernel
and it's simply not because all of the developers are on holiday.
Linux 2.6.39-rc2 is mostly comprised of architecture updates (ARM), various driver fixes, and other random fixes. It's "a small -rc."
It's release announcement can be read at LKML.org
While this release candidate is not too exciting, the Linux 2.6.39 kernel introduces some exciting changes for new drivers, open-source graphics DRM updates, etc. At the time though, we're already looking forward to the Linux 2.6.40 kernel