Fascinating.
Someone brought up that the pointy teeth guy from the MOS mini has an atomic axe looking thing. That go me thinking that with Bendis being super into the Legion, now actively using Supergirl and Superboy in his run, the Legion coming back into play, and Phantom Girl's ancestor being in present DCU, it's totally possible that the framing device for this six issue mini will be time travel. That might be where the retro S comes from, and the vehicle for Bendis to both get a definitive recap on the history of Superman, and "uncover" some hidden truths that will be followed up in his run.
It's a thought.