It's going to come down to a ideological battle between Manhattan/Ozymandias and Superman. Manhattan is the cold, hopeless detachment (a major criticism of New 52 storytelling Johns identified was the lack of the relationship and history between the characters after the reboot); while Ozymandias embodies the cynical, manipulative, ends justifies the means superheroing that was mimicked relentlessly and poorly after Watchmen. I think the overall point of this as a response/companion to Watchmen is not to deconstruct Superman like Moore has in the past, but to argue that the strength of these characters is their hope, relationships, and history.

I'd be really surprised if the climax of the series is an actual battle between Manhattan and Superman actually.

spoilers:
I think the story will definitely go down the road of taking Superman down in status within the DCU, given the events of No. 8, but ultimately we will see that through his relationships, not only with Lois, but with Batman, other heroes, and importantly his parents, will not become the cynical dark, detached character that Manhattan has become.
end of spoilers