Should we guess that the former is a camera-featured phone while the latter is...ummm...sound/media specialized? Yeah, we like literal names for our devices. Of course, actual specifications and images are missing at this time.
Dell Lightning seems plausible or, alternatively that Asus phone with the AT&T name in the marketplace for that mystery sixth device.
Either way, AT&T customers will certainly have the largest selection of devices for nearly any OS out there. Perhaps they're insulating themselves against that Verizon iPhone rumor?