I am thinking about doing the same, have business in ATL but live in Germany.

Here a text from the DL website shown at the bottom of the new announcement:

Residency: Country of residence is determined by the primary address in the member’s SkyMiles account at the time of qualification for Medallion status. Documentation may be required for some types of address changes. Please see the SkyMiles Membership Guide for more information and a list of acceptable documentation. Delta reserves the right to audit an account at any time for residency requirements, request further supporting documentation and update the address for any member's SkyMiles account using the National Change of Address (NCOA) data filed by relocating postal customers, but shall have no obligation to do so. Accounts found in violation are subject to penalty, up to and including termination of Medallion status and closure of the SkyMiles account.