Don't know if this will benefit you, but I found some information on the Hibernate 4 Webinar page. In a linked doc they also gave some links. I have not had a look at them, but maybe give them a go:
I can't paste the answers here because I don't have enough reputation points to add more than two links in the answer (I really need spend more time on this site) :(
So, I wrote a blog post. Please go there and find the answers. Sorry for the inconvenience.
Introduction of services (see this for more details)
Improved metamodel (not in 4.0.0.Final yet, we planned this, but due to the tasks are more than we expected, and it would take too long
to get 4.0 out, so we decided to move this out of 4.0.0.Final but will
be upcoming release soon see this for more details, and this is a
design document)
Initial osgi-fication by package splitting (public, internal, spi)
Support for multi-tenant databases (see this for more details)
Migration to i18n logging framework (using jboss logging)