Well, it looks like Lex Luthor will be having a close brush with Death of the Endless in Action Comics #894, and not Swamp Thing as I recently speculated. That's obviously an even bigger coup for Paul Cornell, and apparently he has Neil Gaiman's blessing to use her, so the legendary Vertigo embargo will be broken for the first time in twelve years as Lex crosses over to the Other Side in his ongoing arc. The "Other Side" being Vertigo or the afterlife, depending on how you look at it. Sandman characters last crossed with the DCU in 1998's JLA #22, when Daniel, the then-new Dream led the JLA into the dreamworld to combat a Starro creature invading humanity's subconsciousness.
My, how time flies. Why, that's way back when DC was still pretending that Kyle Rayner was going to last as Green Lantern:
As I recall, Grant Morrison was a Kyle-as-Green Lantern booster, as was I, but we all know how that turned out. Back to the subject at hand, I like to see some crossover between the DC and Vertigo universes. Let's see if Action Comics #894 opens the door for more.