With Daenerys Targaryen losing touch with her empathetic side and slaughtering millions of innocents at King's Landing, it seems all but certain that Jon Snow, AKA Aegon Targaryen, will go to battle with his aunt/former lover. He likely won't be the only character to turn on their queen, as dissent now runs rampant throughout Dany's ranks.
"The Bells" made clear that Davos was sickened by Dany's sacking of King's Landing. Not only have past episodes proved his affinity for Jon, but he's opposed to excessive bloodshed. Those two stances combined make him a likely candidate to support Jon's cause.
Sansa made her feelings about Dany known to all - she even told Tyrion of Jon's true lineage in hopes of sparking a coup against the Mother of Dragons. Even if Sansa is working from the sidelines, she'll be working in Jon's favor.
The conclusion of "The Bells" seemed to indicate Arya has a new mission: to take out the "Mad Queen." She has already voiced her concerns about Dany's leadership abilities in the past, and in all likelihood, Arya would gladly eliminate Dany in favor of her cousin-brother's ascension to the Iron Throne.
If Sansa and Arya are going into battle, it's almost a guarantee their most staunch defender will fight alongside them. Brienne swore an oath to protect the Stark women, a promise she will no doubt keep until her final breath.
Sam made his allegiences clear in "Winterfell," the first episode of Season 8. He doesn't trust Dany, he doesn't condone her burning of his father and brother, and he thinks Jon is the best leader he's ever known. His support for Jon is almost a foregone conclusion.
Podrick always fights alongside Brienne - if Brienne joins the fight to oust Dany, Podrick will likely do the same.
Having seen what Dany is capable of in "The Bells," Tyrion may decide it's time to shift his loyalties and back Jon in his campaign to take the Iron Throne.
While Gendry has Dany to thank for his legitmization and his new lordship at Storm's End, he also bears a torch for Arya, and if she needs his help, he will readily go to battle against the woman who rechristened him.
In "The Last of the Starks," Tormund left Winterfell to take the Free Folk back to their home beyond the Wall, seemingly bringing an end to his fighting days. If he feels Dany is a threat to his people, however, he may join Jon in battle once again.
While Bran's motivations have been murky since he became the Three-Eyed Raven, and while he's had a more hands-off role in all the previous battles, the eldest surviving male Stark might put his warging powers to use against Daenerys.
Yara did reclaim the Iron Islands in Daenerys's name - however, if she feels the Mother of Dragons is a threat to her home, she won't hesitate in backing Jon in a campaign to overthrow Dany.
Bronn has no moral compass and only supports those who can benefit him in some way. While remaining loyal to the most powerful woman in Westeros would be in his best interest, he also thirsts after his lordship at High Garden. If Tyrion tells Bronn he's more likely to get what he wants under Jon's kingship, Bronn won't hesitate to assist.
Grey Worm is an outlier in this case. He has proven himself to be a fierce supporter of Daenerys, though he may decide to switch sides if he realizes she no longer cares for the underprivileged and enslaved.