Note: This post is based on Beta 2 and is subject to change in future releases.
As you already know when upgrading a MOSS 2007 farm into SharePoint Server 2010 farm using db-attach method, by upgrading the SSP database using New-SPProfileServiceApplication cmdlet only user profiles can be migrated and rest of the settings for Excel services, My Sites, Search and BDC should be manually applied to new environment. for more information look at Perform post-upgrade steps for a database attach upgrade (SharePoint Server 2010) and How other services are affected by upgrade (SharePoint Server 2010)
Due to changes in SharePoint Server 2010 Business Connectivity Services (BCS) architecture and model’s schema changes, existing ADF files cannot be imported post upgrade. While these ADFs can be recreated in new environment using SharePoint Designer 2010, this may not be a feasible option specially if you are dealing with large number of models in your farm.
To overcome this issue, since In-place upgrade migrates all the SSP settings including BDC the following steps can be considered to import the migrated MDF files to your new SharePoint 2010 environment:
1. Setup a single box 2007 SharePoint environment
2. Do an in-place upgrade of that single box environment
3. Export BDC models from there
4. Import BDC models into freshly installed SharePoint 2010 production environment