Felicity moved on to a new boyfriend but he wound up murdered by the Green Arrow in the mideason finale. However, Felciity won't blame Oliver and will instead focus on taking down Prometheus,
resulting in a possible shift to the dark side.
As far as the Laurel Lance cliffhanger, the promo for the midseason premiere pretty much spoiled that it's actually Earth 2's Black Siren, not Laurel in Team Arrow's lair. However, showrunner Wendy Mericle says the Siren's presence and her resemblance to the Laurel that Oliver used to love will have a major impact on Oliver and Felciity moving forward. "
[Seeing Laurel (?!)] is a very welcome surprise but there will be… whatever the reverse of a ‘silver lining’ is… when he finds out what’s really going on. It will have a lot of emotional resonance, particularly for him and Felicity.”
Back in prison, Spartan aka Diggle will begin to grow closer to Vigilante as he finds a renewed focus to find answers. “
[Diggle returns] with a much bigger drive, and not the same fatalism that he had earlier in the season. He’s going to come up against Colonel Walker [and] grow closer to Adrian Chase.”
As previously reported, Talia al Ghul factors heavily in solving the Prometheus quandary, perhaps an indication that he's undergone training at the hands of the League of Assassins. That would certainly explain why his costume bears such a striking resemblance to Malcolm Merlyn's Dark Archer.
One final note from Mericle is that Oliver will develop a strong bond with CPD Detective Tina Boland. What that means for Earth-2 Laurel Land and Felicity Smoak is anyone's guess.
Arrow season 5 returns Wednesday, Jan. 25 at 8/7c on The CW with an episode titled, "
Who Are You?"