The latest episodes of Arrow raised an interesting question regarding the future Felicity Smoak and what would apparently prompt her to hide her daughter's existence from her former Team Arrow teammates. The answer may lie in the Green Arrow comics and a prophecy involving a villainous group that seems to be on the verge of revealing their existence in the Arrowverse.
Arrow season 7 episode 13, "Star City Slayer," ended with the shocking revelation that Blackstar was Mia Smoak, the daughter of Oliver Queen and Felicity Smoak. The next episode, "Brothers and Sisters," continued to deliver astonishing developments, as Dinah Drake, Roy Harper, and William Clayton revealed that none of them knew that Felicity had ever had a daughter. This was doubly perplexing as "Star City Slayer" revealed that Felicity was pregnant and "Brothers and Sisters" ended with Felicity telling Oliver the good news. Finally, Mia revealed that she had never known her father and all she knew of Green Arrow came from old news reports and her mother's stories.
The revelation that Mia Smoak grew up without knowing her father, Oliver, was stunning enough, but the fact that she grew to young adulthood without any of her father's former allies, apart from John Diggle, knowing about her was truly amazing. While Arrow season 7 had seen Felicity growing increasingly security-minded after her near-death encounter with Ricardo Diaz in the season premiere, and the characters who knew her in Star City 2038 spoke of her becoming increasingly paranoid over the years, there was no apparent reason why she should need to hide her daughter or why Mia Smoak would feel the need to adopt the Blackstar alias. This begged the question - what would require such drastic measures?
The answer becomes apparent if we consider the theory that the terrorist group run by Dante in Star City 2019 is the same one plotting to blow up Star City in 2038. While the name of this group has yet to be revealed on Arrow, it seems to be based on a group from the Green Arrow comics called the Ninth Circle. A satanic cabal of criminal financiers led by a man known only as Dante, the Ninth Circle are also notable for having a prophecy regarding the Queen family line.
In the comics, as Oliver Queen fought to expose the Ninth Circle and thwart their designs to take over his city, he was stunned to learn that not only had his father been a member of the Ninth Circle but his ancestor, Robin Queen, had been the Ninth Circle's founder! A robber baron of the old school, Robin Queen believed in unregulated capitalism, legalized slavery, and the acquisition of power for power's sake - and he had founded the Ninth Circle as a quasi-mystic order built around his ideals. It was written that the strength of the Ninth Circle was dependent upon a member of the Queen family always being at its center, and with Oliver having been judged unworthy due to his activities as Green Arrow, the Ninth Circle became obsessed with the capture and conversion of Emiko Queen - the only other surviving heir of the Queen bloodline.
The fate of Emiko Queen in the future of the Arrowverse is unknown, but "Brothers and Sisters" revealed that Dante is already aware of her existence. Assuming that something happens to both Emiko and Oliver Queen in the future (as many have, given the anticipated ending of this year's Arrowverse crossover event), it's entirely possible that Felicity Smoak could soon find herself carrying the last vestige of the Queen family bloodline and with a powerful clandestine society hunting for her. Should that be the case, it would make sense that Felicity would hide herself and her daughter with only John Diggle (who knows of the danger of Dante's group) knowing their secret and Mia Smoak growing up hiding her true name and nature from the world. Future episodes of Arrow shall reveal the truth, one way or another.