The first release of a Geology Data Model for ArcGIS software is due this Fall, perhaps late October or early November, according to Geoff Wade with ESRI.
ESRI is a partner with the AZGS-led Geoscience Information Network (GIN). Integration of GIS capabilities with the growing "geoweb" resources of online data and webservices was a major theme at last week's ESRI User Conference in San Diego, which draw over 14,000 attendees.
I presented the GIN project on Thursday morning but most of my time was spent talking with companies interested in participating in GIN, mostly as users or application providers.