I’d go with MSP, actually, whether flying in/out or just through. I’d also rank DTW above ATL as a through airport.
But yea, switching hubs is a whole protracted and intensive process (it took several years after the Northwest/Delta merger just to “de-hub” Memphis and Cincinnati), so I highly doubt Delta up and abandons one of their six primary US hubs over these small-fries. By the time they even had a plan in place, there might be a more favorable administration at Georgia’s helm.