Re: DC's New 52: Reviews and Discussion (Spoilers welcolme and likely)
The modern Dr. Mid-Nite, Pieter Cross dated Black Canary during the period where Ollie was dead. He stepped aside when Ollie returned.
His predecessor, Dr. Charles McNider was one of the few Golden Age characters never associated with a woman (Jay had Joan; Alan had Molly & Rose Canton, Jade and Obsidian's mother; Carter had Shayera; Al Pratt, the Atom, had Mary James; etc.). There was a fan theory, that DC squashed, that McNider was in the closet for most of his career.
Andy Mangel's website just lists Dr. Mid-Nite under "proposals" but doesn't elaborate on it.
In 1999, gay comics-writer Andy Mangels proposed a story for DC’s anthology title Legends of the DC Universe. In this story, an old lover of Dr. McNider’s, now living in a retirement home, would come forward with the story of their “love that dare not speak its name”, finally revealing once and for all that Doctor Mid-Nite was, in fact, deep in the closet back during the Golden Age. Hey, at least he could see in that closet!
DC editorial nixed the idea, for reasons unknown. While it was one thing to create new gay characters for the comics medium, something DC was pretty good at doing, maybe they weren’t ready to out one of their original characters just yet – even if it was one that no one really cared about like Doctor Mid-Nite.
"When I reach for the edge of the universe, I do it knowing that along some paths of cosmic discovery, there are times when, at least for now, one must be content to love the questions themselves." --Neil deGrasse Tyson