There have been rumours lately that Black Canary will show up in Justice League and that the character's stint in Arrow is coming to an end as a result. Whether there's any truth to that latter point remains to be seen, but Laurel Lance is definitely someone who should be making their presence felt in this superhero ensemble. A great female character, she would be an unexpected addition, but having a wild card is no bad thing. While most of the team are there to set up their respective solo franchises, Black Canary is a character who could open the door to everything from a Birds of Prey movie to something Green Arrow related. Her sonic scream (which is an actual scream in the comics, and not something achieved via technology a la Arrow) makes her very formidable, so there's really no reason to think that Laurel couldn't fit nicely into this team.