Warning! The following contains spoilers for Black Lightning's Season 2 finale.
In the midst of an action-packed Season 2 finale, a Black Lightning character made a reference to a DC hero that may have teased the show's oncoming connection with the rest of the Arrow-verse. The moment came when Thunder and Lightning were treating an injured Gambi, and had to strip him out of his cover armor. When Lightning asked if he was going to be okay, Thunder responded by referencing The Dark Knight.
Pssh... I wouldn't be surprised if he told us he was Batman.
The reference isn't all that strange considering Black Lightning is a part of the DC family, but the timing behind making a Batman reference now is somewhat odd. The character has been referenced on Arrow-verse shows before, and got a handful of mentions in the "Elseworlds" crossover late last year. Was Black Lightning's Batman reference an acknowledgement the hero exists in their universe? If so, this could be a hint Black Lightning is finally merging with the other shows.
The key word being "could," of course, because this wouldn't be the first time Black Lightning has name dropped a character active in the Arrow-verse. Vixen was mentioned back in Season 1, and despite her appearances on Arrow and Legends of Tomorrow, Cress Williams' hero has yet to grace any other of the Arrow-verse shows.
Additionally, Black Lightning has featured DC Comic publications in the past, such as DC's Outsiders. Batman is the founder of that superhero group, which could mean he does exist in Black Lightning, but only as a fictional character. Bruce Wayne has been confirmed to be an actual person that exists within the other shows, so if he's fictional on Black Lightning this may confirm the show doesn't exist on the same Earth as Flash, Arrow, or Supergirl.
That's probably the case anyway, as Black Lightning's showrunner Salim Akil has been pretty upfront about crossovers on Black Lightning. Put simply, he's stated that the only way it's happening is if the other characters come to Freeland. Arrow star Stephen Amell thinks differently, however, and stated a year ago a crossover is more or less inevitable at some point. If he's right, this mention may have been the show's way of laying groundwork for a "Crisis" appearance next season.
The world will have to wait for an answer, although one would think this will probably be addressed before Black Lightning returns to The CW for Season 3. After all, Arrow-verse fans go crazy for Batman-related news, especially when there's a tease he might appear in some form on The CW. In fact, The Flash made a Batman reference not that long ago, although it features the character in a role not many are familiar with.