My situation is that one of the sites in my client's enterprise already has Unity v4.0.5, and works fine the AD was previously extended.
Question: we're now adding Unity v7, does the AD have to be extended again? Or is the existing AD good enough? If it has to be extended again, how will it affect the existing Unity v4.0.5 installation?
you do have to extend the schema, the schema only adds info, it does not remove anything and is backwards compatible. it will only add fields to be used by 7.x which will be transparent to 4.x
if this helps, please rate