I can attest that D.Z. is quite familiar with Generations, Death Metal, Rebirth, Doomsday Clock, and Multiversity. As am I. Of them, only Death Metal featured a change to the Orrery of Worlds. The only other events DC has published which have messed with the Orrery of Worlds are 52 (which created it) and the New 52 initiative (which altered it offscreen). Possibly Final Crisis as well; though the changes it brought about were limited to Earth-0 as far as we can tell (we're never shown any repercussions on any other world in the wake of Final Crisis; only the addition of Red Circle and Milestone to Earth-0 continuity), and even those changes have fallen by the wayside. Generations introduced the Linearverse; but that's not in the Orrery. Rebirth, like Final Crisis, appears only to have affected Earth-0, not the Orrery. Doomsday Clock introduced Earth-1985 and Earth-52 and implied others; but like the Linearverse, they're not in the Orrery. And Multiversity retroactively defined the changes that the New 52 had wrought.
I don't doubt that Dark Crisis will be changing things up in the Omniverse. We're hours away from seeing what's going to happen to the Orrery; and at least one of the previews suggests that the structure of the Orrery of Worlds is about to be shattered. But D.Z.'s point that the worlds that have been in the Orrery will live on is valid: even if the Orrery is destroyed, those worlds will find new homes, either among the newly reborn Infinite Earth, or in Hypertime. Or both.