This whole thread brings me back to a previous discussion about the new multiverse. Remember back in Ion #10 this quote:
"So many worlds. Why shouldn't they all get a chance to live?" - Captain Atom (Monarch)
What did Captain Atom mean? According to 52, there is now a multiverse of only 52 distinct universes, no more no less. We also know the Book of Eternity continues rewriting itself, the Tangent Universe exists, Bronze Age Legion of Superheroes are back in Superman's continuity, Superboy-Prime is still a leftover from the original Crisis, the Bleed connects universes together, and at some point, all universes contain analogous versions of Superman, Batman, and Wonder Woman.
I believe post-Countdown, the next Crisis crossover will deal with Captain Atom's statement, the Monitors, all 52 universe, and the realization this multiverse is part of something much bigger than first realized. Frankly, the only way to write this correctly is to revise Crisis on Infinite Earths.
Update
Okay, I read 52 #52. Earth-17 is a weird medieval post-apocalyptic world with armored knights riding albino mutant horses. Earth-3 is an updated pre-crisis Earth-3 with a CSA Martian Manhunter. Earth-10 resembles pre-crisis Earth-X with Freedom Fighters battling a Nazi Justice League of America. Earth-50 is Wildstorm (WS fans must love that). Earth-5 is the very Fawcett Marvel Family battling Mr. Atom with Uncle Dudley and Mister Tawky Tawny looking on. A poorly painted Kingdom Come Earth resides in Universe-22. Earth-2 appears to be a continuation of pre-crisis Earth-2. Charlton Comics' The Question, Nightshade, Dan Garret Blue Beetle, Captain Atom, Judomaster, and Peacemaker all reside on Earth-4. New Earth, current DCU "clutter" Earth is pretty much Earth 52 with other Earths designated Earths 1-51.
One confusing scene, at least to me, is when Booster Gold travels back in time to "borrow" Ted Kord's scarab. The place is New Earth but it's one day after Crisis on Infinite Earths. I don't remember post-crisis Earth being designated this way. I thought it was a post-IC thing.
Possible spoiler for Countdown or next Crisis
http://romney.homestead.com/files/Megaverse.jpgUpdate 2
Booster Gold, don't you just love saying it?
http://www.wizarduniverse.com/magazine/wizard/004446523.cfmhttp://wizarduniverse.com/_images_/004446/BoosterGold1.jpgWizards 52 Roundup with Pics
http://www.wizarduniverse.com/magazine/wizard/004448945.cfm1) "EARTH-1: The so-called “new Earth” is pretty much the DCU we’ve known since the end of Crisis on Infinite Earths with a few key tweaks (Wonder Woman as a JLA founder, etc.)."
That is not what is implied in 52 #52. Rip Hunter states, " Together we are the only ones that can save New Earth and Earths 1-51..." According to Rip's quote, New Earth may as well be Earth-52. DC would never change a comic already printed.
http://jigsawmen.googlepages.com/thecollectededition 
2) “There was some resistance to bringing the multiverse back from the boss, but we felt that it was more about the idea that we would keep our Earth intact and doing something new instead of going backwards,” expounded Johns. “You could do lines and specials and miniseries about what these other universes are like. For example, Mark’s a big proponent of thinking the Marvel Family works best in its own reality. And now I want to see him do that.”
Dan Didio must be the boss. You know, I don't believe DC intended to bring back the multiverse until after Infinite Crisis finished. See collected edition link above.
To Mr Johns: Moving forward instead of going backwards creates more confusion or vice versa.
There is possibilty of Mark Waid writing a Captain Marvel Earth-5 book?!
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