It is as I (among others!) deduced, demanded, and dreamed:
the Multiverse is back.
Or, perhaps, was never gone to begin with.
As previously mentioned, I think the original undoing of DC's multiverse was a serious error. I hold this opinion not because I'm some Thomasian fanboy who has to believe that everything he's ever read in a comic book "really" happened. I hold this opinion because the multiverse is a firm yet flexible structure for helping readers and writers handle the long-term problems of a 70 year old and growing storyline with some characters that are fixed in time and some that aren't.
Don't get me wrong. I'm delighted that many characters previously kept separate on other earths -- such as the Marvels, the Freedom Fighters, and the Charltons -- are now part of the DCU proper. But the hard truth is, one universe just isn't big enough to contain the DCU. And that's a high quality problem, one I enjoy having.
You can -- and I'm betting some of you will -- comment on how much easier, healthier, and sensible it is to have a monoverse. Don't waste your digital breath. For the sake of argument, I'll even concede all your points are valid. It just doesn't matter.
A monoverse created through the contributions of many people over many years focusing on many different characters will inevitably lead to continuity conflicts. What begins as a fresh start will tighten every year as the storylines expand, and wind up as a confining straightjacket. A multiverse allows you to either parcel storyline out into various parallel worlds or reboot occasionally, starting on a "new earth".
The multiverse is back. The more you struggle against it the more it hurts, so just relax and enjoy it.