Those are operated for vacation charters, not actual G4 service. They plan to run their own branded international flights starting next year.
It doesn't matter if G4 is flying their own branding, flying for Apple Vacations, or some other vacation group. The point I'm trying to make is that G4 already flies international into CVG today. They already park at B, offload their passengers, and then tow over to A. They need not wait until some fantasy customs opens up in A before they start.
By law, all carriers have to have access to FIS. Since there is no way to bus people from a remote parking spot over to customs, DL has to give up a gate when an international plane arrives. Whether they like it or not. Over the years, I've seen the P&G Brussels charter, Ryan Air 777 on some company outing, the Bengals on VS, Air Canada stopping to clear a hockey team, medical emergency diversions, etc, etc, etc. All parking somewhere at 1-10. Heck. Ive even seen inbound international UPS cargo planes parking at DL's gates, when SDF was shut down for weather, just to clear the crew.
The last few months of flying out of CVG, I've noticed that gates 3 and 4 seem all but abandoned. There is no more ground equipment staged at those gates, and I think I've only seen one RON at 4 once. Those are 2 gates I'm sure DL will rent out to international arrivals, since they don't seem to use them anymore.
I have been keeping track, DL uses a peak of 21 gates at a time for deplaning/cleaning/boarding, this does not including RON/idle aircraft. With international carriers deplaning at Concourse B, especially when Allegiant adds international flights and if an international carrier comes, that mean DL probably wants an extra overflow gate, totaling 22 gates used. That would allow them to give up 6 gates without affecting their operations, but it would require them to use the RON pad when aircraft are not flying.
If you park at the observation point on Donaldson Rd, you can see the end gates (26, 27, etc) being used for charter flights and maintenance needs. If a baseball or football team flies DL or UA (it appears that UA charters are handled by DL ground people in CVG, not their own people), they will park at the end of B concourse. Many times, you will see a CRJ land, pull into that end of B, and then have maintenance proceed to work on it for the next few hours. If DL were to give up those end gates, they would have to move the charter and maintenance parking flights somewhere else. Will they fit into the remains gates? If I remember correctly, DL owns the building, and have a lease on the land until 2020. So what would be the incentive for DL to give up gates?