Hmm so the normal ant task also doesn't work (HibernateToolTask)? That's in fact more of a jboss tools question, where is a version compatible with hib4. Maybe you can try asking on their forum?
You can always try hbm2ddl.auto=update .
The normal HIbernateToolTask does not exists anymore in the hibernate 4.x distribution. And it seems that the new jboss tools currently don't support envers in anyway. You can generate everything except for envers related audit tables, etc. They don't seems to have any timeline available when envers will be supported as far as i know.
The only way i found is to downgrade dependencies to hibernate 3, then generate everything based on hibernate 3 and it's tools and then upgrade back to hibernate 4. Which is annoying if you have any custom types, since the method signatures got altered there ;-).
So if you use envers and want to change your database in the near future, my only advice is do not upgrade to hibernate 4 yet. Atleast until tool support is fixed, it saves you a lot of frustration.
Sorry to hear that.
My only suggestion so far is to try to fix this yourself and contribute