I think we can all agree that the ending of Arrow 5x09 caught us off guard when Laurel Lance / Black Canary came back to life, but is it really her? I am like 92% convinced that the Laurel we saw is really Earth-2 Laurel / Black Siren. I think her appearance given that everything that just happened is far too convenient especially when there’s a homicidal maniac hell bent on destroying Oliver’s life running around, so why let up now? When something sounds too good to be true it usually is. I think Prometheus somehow found Earth-2 Laurel and convinced her to masquerade as her Earth-1 doppelganger to give Oliver false hope, that he’s been reunited with the love of his life only to later learn it’s not really her. Or alternatively Laurel-2 could simply have escaped the pipeline herself and is trying to take her doppelganger’s place to hide in plain sight.
If this is right what I hope happens is she finds redemption for herself, after all Earth-1 could be a fresh start for her, and grows genuine about Oliver’s cause and becomes the next Black Canary. Laurel-1 did make Oliver promise back in 5x01 not to let her be the last Canary, maybe this is how he could honor that last request by helping Laurel-2 to find her way back from evil. It would also be more faithful to the comics in terms of appearance as Laurel-2 is a meta-human from Earth-2 just like the actual Black Canary from the comics is. A nice further addition would be if she was also re-named "Dinah Drake" like the original Black Canary so we don't have to call her Earth-2 Laurel or Laurel-2. It would be interesting seeing Arrow utilizing Multiverse for a change rather than just Flash, after all what's the point of having a shared universe if they don't borrow each other's resources?
Wendy Mericle did say that "Laurel Lance will return alive and well and Flashpoint may have something to do with it", but remember the producers either lie or twist their words all the time. Mericle said Laurel will return but she didn't specify if it was Earth-1 or Earth-2, and she didn't say she'd return back from the dead. She also said Flashpoint may have something to do with it, maybe she means that Earth-2 Laurel wasn't imprisoned in the pipeline like before and may have escaped before Barry could detain her. Yes many people think Flashpoint could have spared Earth-1 Laurel but that means she wouldn't have been dead to being with and she'd have been with Team Arrow this whole time, yet she's only been in one flashback and a dream sequence. Unless they bring Speed Force and time remnant crap into it, assuming that even applies to non-speedsters, I don't think Flashpoint is going to bring Laurel back.
Alternativley people have speculated that Sara is going to kill the 1987 Damien Darhk. However if she did Season 4 would be erased and yet right now the events of that season still remain intact, Laurel's death included. If the 1987 version of Damien is going to die later on in Legends it already would have occured in the timeline, as he is 30 years younger than his Season 4 self. This means he never would have been around during Season 4, and as noted above Laurel wouldn't have been dead to begin with, yet she still is. True alterations sometimes take time to take effect and they could explain it away with some time remnant crap, but Sara would have had to already killed Darhk for that to occur. Even so this would still have the same result of Season 4 being erased Laurel's death included, which means she wouldn't be dead to begin with again. No matter how you look at it there is no way Sara can bring Laurel back without screwing things up and the last thing we need is Flashpoint 2.0.
Yes Laurel could have faked her death to begin with but there are many implications against this. Why drop off the grid for 8 months and let her family suffer through grief, and why make Oliver promise to find someone else to be the next Canary if she's gonna come back anyway? If she has faked her death and it was to protect Quentin from Damien Darhk then yea that I could roll with that, but she would have returned after he died like maybe a few weeks later and it’s been 8 months. Rip Hunter has also confirmed that Laurel stays dead, which Vandal Savage only further implies to be the truth. Faking her death just raises too many questions that are just too out of character for Laurel.
The timing of her appearance is way too convenient given what has just happened. Oliver just killed Billy by accident, Diggle has been apprehended by the authorities and Evelyn has betrayed the team, and yet Laurel shows up now of all times? When she appeared and turned around and said “Hi Ollie” she kinda sounded kinda nervous and she even twitched a little like she’s playing a part and hoping she doesn’t screw up. Which brings up the question why would she be nervous around him? True she may be responding like “yea sorry I've been gone and I've got some things to explain...” but I still don’t think Laurel-1 would fake her death and drop off the grid for 8 months and let her family suffer as they have. But if it was Earth-2 Laurel playing the part this would explain a few things.
Another more simple answer is Laurel-1 was brought back in a Lazarus Pit. We know Talia al Ghul is going to appear soon and her actress Lexa Doig is 43, yet Talia must be into her late 50s to early 60s based on her 1960s appearance in LOT 1x09 meaning she must have a Lazarus Pit. But why would she bring Laurel back? True she could have brainwashed Laurel or is giving Oliver false hope and is planning on killing her again. Again this just raises the question as to where Laurel has been this whole time, or why would Talia bring her back now of all times? Besides I personally think this is how Tommy could be Prometheus. And also Sara has access to information in the past and the future onboard the Waverider so if Laurel was going to come back she would have learned of it by now, and she would have told Oliver and Quentin. I think a Lazarus Pit would be way too simple and predictable. Furthermore if there is more than one Lazarus Pit that just means anyone can come back and death wouldn't be taken seriously in this show anymore.
This is just a theory but just looking at facts we know, Earth-1 Laurel is dead and Earth-2 Laurel is alive, I think we can assume it’s Earth-2 Laurel. Earth-2 Laurel becoming the next Black Canary has been speculated for some time now and the producers do usually listen to us, unfortunately they listened to the wrong stuff and decided to do Olicity. Ugh! Maybe this time they could get it right and adopt a theory and storyline more than a few fans have speculated, of something that’s actually interesting. If they did I'd forgive them for Olicity.