User blog comment:Gifist8/Black Lightning Confirmed For CW!/@comment-30655988-20170330192418/@comment-27700324-20170330195354

My theory is that the first crossover will actually be with Supergirl. It is logical for them to do this because Black Lightning fights crime in Metropolis's Suicide Slums. The only Earth to confirm Metropolis's existence is Earth-38. I'm guessing Black Lightning knows Superman and maybe Supergirl has also known the hero. So whenever there is another alien invasion or if the multiverse is in danger, Supergirl can bring J'onn Jon'zz and Black Lightning to help.