I'd prefer they take the Marvel approach of simply never mentioning it again, but I would also be happy with a single line of dialogue handwaving him...
New 52 Superman was kind as hell to the people, while retaining an older edge when it came to what he was fighting. Him being kind doesn't close the...
"Mark my words! This drill will open a hole in the universe. And that hole will become a path for those that follow after us. The dreams of those who have fallen. The hopes of those who will follow. Those two sets of dreams weave together into a double helix, drilling a path towards tomorrow. THAT's Tengen Toppa! THAT'S Gurren Lagann! MY DRILL IS THE DRILL THAT CREATES THE HEAVENS!"- The Digger
We walk on the path to Secher Nbiw. Though hard fought, we walk the Golden Path.