Per Brian Hibbs, he got a call from Someone Who Should Know, who confirmed that the 52 books are indeed all ongoings.  That said, two words:  DC Explosion.  :-)  Or to be less snarky about it, attrition is bound to occur, at varying degrees.

"They're just punching a button that resets the universe back to a more traditional vantage."

Traditional as in "what they grew up with."  Wally was the Flash for 25 years.  Babs hasn't been Batgirl in almost as long.  (Heck, if I'm remembering the years right she just passed the point where she hasn't been Batgirl longer than she was.)  Going by the five year rule, there are generations of comic readers who knew of Superman as a married guy, Kyle Raynor as the one true Green Lantern (or John Stewart for those youngsters who watched the Justice League cartoon), etc. 

If you're going for an all-new audience, I figure it's better to really start from scratch.  Let everyone in on the ground floor together.  Let the folks who liked the last 20 years worth of stuff be in the same boat as the folks who hated it.  Yadda yadda yadda. 

As it stands, anytime I see an announcement from DC that results in a "Yes!!!  The REAL [character X] is BACK!!!!" response from fandom (and I say that as someone who had that very reaction when the One True Legion started appearing again ;-)  ), I think they're appealing to the wrong audience. 

(Edited to add:  Unless we're talking about undoing a story in the last year or two.  There's nothing wrong with a course correction if a Big Change doesn't work out.  I'm talking about the major stuff that actually stuck for awhile.)

Thanks Francesco: Yes, Johns and Reis, i remember having read that yesterday now.

Dave, Stephanie is my second favorite Batgirl after Barbara.

I'm not a huge fan of Oracle.

Plus DC is saying they will have a more diverse cast; you don't
increase diversity by eliminating one of your biggest diverse character.

That said, a more diverse cast indicates we might see new versions of
old characters; Dick Grayson could be a Native American or Japanese,
for example.

If IDW did that with NEXT MEN I'd break open some champagne.

The DC product, on the other hand...well...I won't mind going digital with
Hex...and anything by Ivan Reis is worth a look.