Its a Schrodingers Cat ending. The fate of the world depends the random fat fingers of a fat kid in a grubby t-shirt. You are not supposed to know what happens. Anything could happen. That's the point (I always read it as an endorsement of the Comedian's philosophy, given the badge on the fat kid's sweater - the vagaries of life are funny, even in their extremes).
It's also an endorsement of Dr Manhattan's admonition to Veidt that nothing ever ends. The story began with a stained smiley face and Rorschach's journal and now it looks like its going to start again with those same elements.
Similarly, the whole "clock" metaphor ties into the idea that the same time occurs over and over. It's 12:00 twice a day, every day, forever. The clock keeps going around no matter what.
