Daniel Day won't go near anything like Superman...Besides they already have talked about forgetting that Green Lantern movie ever happen and reboot with the Jon Stewert (Black Lantern).
If Nolan/Snyder were able to get the likes of Russell Crowe, with the right script, DDL wouldn't be out of the question. He did a bullshit musical (Nine) a few years ago, surely a serious Superman film wouldn't be out of the question.
I read a few months ago they were moving forward with a GL sequel.