That said I do think the power struggle between Hux and Kylo should continue since it’s already been established and with Kylo now Supreme Leader, we do need to see a progression and escalation of that.
As long as Hux isn’t redeemed in any way, I’m open to seeing Hux as a mole for the Resistance in Star Wars: Episode IX.
I wouldn’t want this to dominate the story in any way, Hux hasn’t been a particularly compelling or rich character thus far and giving too much weight to his arc as a mole in this final film could take away from more deserving characters.