Since these aircraft are -300ER's, I don't expect to see them flying in the U.S. domestic system. DHL has made several recent statements that they hope to "expand overseas shipments to/from the United States." These aircraft will most likely be flying internationally to/from ILN, LAX/RIV and/or JFK.
It would make a lot of logistics sense for ABX to operate the aircraft, as far as I know they are the only DHL carrier/contractor operating the 767 right now. But that doesn't mean anything in the DHL world. EAT out of BRU is owned by DHL and they currently operate 757's. They could fly the international routes. I would think Transmile (Pacific) might be another candidate. ATI is not in the DHL system right now but their pilots have been hearing rumors of 767's and DHL contracts for a while. DHL doesn't have any qualms about signing up or buying a stake in a new carrier. They don't have any obligation to build up existing carriers and historically haven't done so.
Like MuseumDriver said, though, it's a different direction for DHL to buy new airplanes. Hopefully we'll see more new ideas and all the DHL carriers can prosper somehow.