After migration of the ADB 6.x project into the ADB 7.x project, adbmetadata is  the same as ADB 6.x i.e. it does not get updated.
Even new adapter instance is created in this migrated project, still adbmetadata will not be updated  and will remain the same like ADB 6.x
But when creating a new project in ADB 7.x and then create a new adapter instance, it will show ADB 7.x metadata.

Copy the attached "adbmetadata.aeschema" file, under the migrated ADB project directory as "//AESchemas/ae/ADB/adbmetadata.aeschema"

================== Product: TIBCO ActiveMatrix BusinessWorks Plug-in for Database Version: 7.2 OS: All Supported Operating Systems ==================

The adbmetadata is the aeschema file created while configuring an adapter instance and it is common for all the adapter instances created in the same project.
This adbmetadata.aeschema file is created under "<projectDir>/<projectname>/AESchemas/ae/ADB/adbmetadata.aeschema"

The difference between ADB 6.x and ADB 7.x meatadata:
Following field is added in the ADB 7.x metadata and other fields are same in both versions:
================
This field is added under ADB_SUBSCRIBER_STATUS class.
<attribute>
            <name>NUMBER_OF_UPDATED_ROW</name>
            <attributeType isRef="true">/AESchemas/ae.aeschema#scalar.i4</attributeType>
            <isKey>false</isKey>
            <isReadable>true</isReadable>
            <isWriteable>true</isWriteable>
</attribute>
================ 

To apply ADB 7.x metadata in the migrated ADB 7.x project copy the attached "adbmetadata.aeschema" file under the migrated ADB project directory as
"<migratedProjectDir>/<projectname>/AESchemas/ae/ADB/adbmetadata.aeschema"
Before copy, take backup of old adbmetadata.aeschema file.     

Then open the project with designer, under directory "AESchemas/ae/ADB/adbmetadata/classes/ADB_SUBSCRIBER_STATUS" the "NUMBER_OF_UPDATED_ROW" field will gets updated.