There's been a bit of discourse recently around Az and Gwyn's story that I find a bit odd. It's been theorized that a large part of Az's story will revolve around him getting over Elain/pining for her, while Gwyn waits in the wings and/or pines for him while being a good friend.
That...makes hardly any sense if we consider any of SJM's previous romantic arcs and couples, and the types of romantic stories she seems to enjoy writing. It also makes no sense without the bonus chapter. Many, many people do not read the bonus chapter. Furthermore, SJM's bonus chapter have mainly been used for fun extras. Only Chaol's bonus chapter with Nesryn functions slightly differently - to hint at his future struggles and the fact that they are not end game. But it was necessary for the story we got in ToD.
But let's think about each main SJM couple and the story told with them:
1. Rowaelin. Rowaelin had a significant period of friendship before anything romantic. It defines their relationship. During this time, he was still sad of Lyria, and she was upset over Chaol, but neither one of these issues affected their romantic arc in QoS. In HoF, as just friends, they build the foundation of loyalty and trust, and it was never a situation of either of them pining while the other was still in love with someone else. They were both upset over previous relationships, but those relationships in no way affected their romantic arc, or made it unhealthy. Furthermore, we rarely got any stuff about Aelin pining for Chaol - she just didn't. Az is a different character, but unrequited love/pining just doesn't seem to be SJM's mode of story telling.
2. Feysand. Feysand also became very very good friends before their romance fully started. It was also a friendship based in helping one another and being one another's confidant. Now, while Rhys knew Feyre was his mate and certainly pined for her while she was with Tamlin, we did not have to read about it. Again, SJM is into friendship, not really into writing pining. Furthermore, Rhys was wanting Feyre, so this is not a comparable situation to Az pining for Elain while Gwyn is right there. Rhys pined for his mate. We can expect to see Az also be...really really for his mate.
3. Quinlar. Friends first, lovers second. This fits the typical SJM mold! And again, Hunt has someone in his past, Shahar, but it doesn't affect his treatment of Bryce. Bryce also has Connor. Once their romantic feelings start to develop for one another though, these relationships do not affect their romance. There is no Bryce pining for Hunt while Hunt is into Shahar and Bryce is dejected and sad. Bryce maturely considers that he might still be into Shahar and doesn't get all weird and sad about it. Nor does Hunt ever make her feel like she is second to Shahar.
4. Nessian. Their foundation is less friendship and more based on mutual admiration of the other, and their banter. But still, this relationship really exemplifies what SJM loves to write: sparks. Chemistry. Banter. Electric exchanges.
5. Chaorene. Chaol literally is with Nesryn when he MEETS YRENE. And still doesn't let that affect his treatment of Yrene. Nesryn and Chaol split up, she falls in love, he does too, and neither one of them mopes around for the other or makes it unhealthy.
Why can't Elriel have the lil moment they did have, decide it wasn't worth it or right, and then decide to move on healthily? Why do yall assume SJM will make us read 300 pages of Az lusting for Elain while Gwyn loves him from afar?? Why assume that the QUEEN OF FRIENDS TO LOVERS and MEN STANNING THEIR WIVES would write a story in which Gwyn is subjected to that pain?
Gwyn and Az will likely be friends first, and as with literally every couple above aside from Nessian, they will work through their issues before beginning a romantic relationship.
Az has a LOT to deal with. But imo it isn't specific to being in love with Elain. It's about the way he projects his insecurities and desire for love onto women and thus objectifies them. It's about how he treated Mor and Elain, and about why he treated them that way. Not about his actual feelings for either of them. Az will likely need to work on that before him and Gwyn get together. And he will likely think a bit about Mor and Elain, and he will likely feel sad over them.
But what wont be happening is Gwyn sitting there helping him deal with all of this while she has all these feelings for him. It's more likely that Gwyn and Az, together, will help one another with their problems...TOGETHER. Gwyn has never been in love. Az has also never been in love, either, tbh. Gwyn has never had a long term relationship of love and sex and trust. Neither has Az. They are both well positioned to understand the other's pain. But it does not mean Gwyn is going to be in love with Az while he still wants Elain. I mean what even? I'm sure she won't realize she even has feelings for him until the middle of the book!! Like it's an 800 page long romance novel.
Also, why would SJM write a story about Az in which he pines over Elain, when his mate is right there, if Az's whole thing is that he wants a mate like Cass and Rhys? Why would she do that to him?? It doesn't make sense given how she's written every other couple.
Finally, there's so much discourse about characters deserving to be a first choice etc. Literally no main ship SJM has written, aside from Nessian, has the characters as each other's "first" choice. Feyre had Tamlin. Aelin had Chaol. Rowan thought he had a literal mate. Hunt had Shahar. Chaol loved Aelin and had feelings for Nesryn before Yrene. There is no reason why Az cannot want Elain, decide it's actually not right for him and then have a healthy relationship with someone else. It doesn't make Gwyn a second choice.