I like what this guy wrote on another forum, about Superman fighting CA Superman. I will quote him(credit at bottom)
"
Superman Beyond was a Morrison thing through and through. It focused and expanded on a hyper self-forming story and battle with the Monitors. Superman basically had a better story happening outside the normal realm of thinking, and from his origin he was the basis for an evolving greater story to be told after he beat Mandrakk so to speak. Similar to a writer telling the greatest story ever told while writing a story about it. It fed upon itself in a bigger picture sort of way I guess. Some guy named messhi (or something) tried to explain it that way in a blog review when it came out, like a story writing itself as it unfolded.
The 'to be continued' was meant to symbolize that it wasn't over in an ambiguous & continuous life cycle fashion of birth and death...
Or something like that. It's better to read it separate on your own after Final Crisis. Nobody really got it right in the bigger picture sense, maybe even Grant. The way he writes these days leaves much to individual interpretation. In a weird way, I think it ties to his run on Animal Man (which was pretty good) as far as understanding the 'meta' context. Meta essentially means 'beyond' followed by whatever it may mean to whomever reads it. In Superman Beyond, it may as well tie with the whole beyond theme Grant was going for with both the art and storytelling. Something bigger was happening that Supes was involved in, not just the Final Crisis on earth. He was a part of the bigger story at the time on Earth while being outside of it at the same time simultaneously in an instant or so. I haven't even bothered mentioning Legion of 3 Worlds yet.
To Morrison it was all clear. To many readers, it was just overall initial confusion at the start."
Credit to Name already Taken. from CBR.com