Given Sanji's situation in the newest chapter, I'm chuckling thinking how this might finally come true
Given how Sanji has a habit of sacrificing himself for others, and Gaban's comments, it has been theorized that Sanji has an issue with his own self-worth (given his heritage and upbringing) which is what is holding back him unlocking his Conquerer's haki.
And since the chapter ends with Sanji in distress as he remembers his time with Ivankov, I've seen some discussion that Ivankov and the newkamas tried teaching Sanji self-acceptance (something which LGBT folk are very knowledgeable about), through encouraging him to try out being a newkama, Ivankov temporarily transforming him into a woman, or just through sharing their own queer experiences.
Either way, I've long loved the idea of Sanji's time with the newkamas being used for more than just a gag, since it presents a more respectful picture of the newkama, provides a great opportunity for Sanji to reflect on his own troubled relationship with queerness, masculinity and women, and plus the idea he's been hiding a made-up right eye for years is fucking hilarious to me.
And it seems like now Oda's finally heading in that direction: in order to unlock CoC, Sanji has to accept the lessons he learned from Kamabakka Island, and in doing so accept his own self-worth, in direct parallel of queer people accepting themselves.
Just imagine him doing a Death Wink, and the black lightning erupting from it.