Arrow season 4 was one of the most emotionally charged and heart-breaking in the history of the show. There have been many deaths on the show – Tommy Merlyn (friend of Oliver & Laurel’s lover), Moira Queen (Oliver’s mother), Robert Queen (Oliver’s Father), Thea Queen (who was killed by Ra’s Al Gul and then brought back through Lazarus pit), Sara Lance (who was killed by Thea under the influence, later was brought back by the pit and her soul was restored by John Constantine). But Laurel Lance a.k.a Black Canary died a painful death and consumed everyone with grief. In fact, a new character called Evelyn Sharp (it’s Evelyn Crawford in DC Comics) donned the mantle of Black Canary in order to take revenge from Damien Darhk and RuveDarhk for the murder of her family, but now she is working with Prometheus.
The mid-season finale of Arrow season 5 had a major shock in the end when Laurel Lance unexpectedly showed up. A Reddit thread whose predictions have been bang on till now is saying that she is Laurel Lance Earth-2 dopple-ganger, Black Siren. Also, there is going to be a new recruit for the Team Arrow in the second half of the season and apparently she possesses canary cry powers. There is an insane theory that Felicity Smoak could be the next Black Canary.
Guggenheim talked at length in an interview about the possible darker path for Felicity Smoak going forward:
As with all things Arrow, it’s not initially what you think it is and it will ultimately relate to the overall season theme of legacy, but in this case something very specific to Felicity.
This is something I was talking to the writers about in the writers’ room — Felicity is a wonderful character because she brings some light into the show. So it’s a darker — it’s an edgier story for Felicity, but at the same time, it’s still Felicity. You want to keep the character.
It’s the sum of a bunch of stuff, and Billy was sort of the final straw. It’s also the sum of the fact that Felicity’s been living in this darker world for the last four-plus years now and one of the things we’re exploring is how much what Oliver and Diggle and Roy and Laurel have been doing as vigilantes affected her and affected her way of thinking about things.