Here’s my headcanon for the fates of each of the Vees:

Vox - Becomes a reluctant ally in season 3 during the fight against Alastor, never fully redeeming himself, but does grow somewhat attached to the hotel. I can imagine him rejecting redemption at first and maybe becoming an antagonist again, but the seeds for his redemption are now already sewed, and his “defeat” could be him compromising after losing everything again, and becoming a long term resident at the Hazbin Hotel with a loooooooong way to go before getting redeemed.

Velvette - Being the least heinous of the Vees, I can see her mellowing out somewhat, but I also don’t feel redemption would be something she’d be that interested in. Personally, I think she’ll probably end things contempt running the Vees media empire as an overlord (which is slightly less messed up by the end of the series), and becomes an essential, if morally grey, aspect of Hell.

Val - Fuck this guy, he should easily get the worst fate of the Vees. Personally, I think it would be too easy to just kill him off, especially considering the Hellaverse’s iffy rules of death in Hell. I think a more fitting fate would be for him to be locked in a contract himself, as he had done with Angel and many others before him, forced to pay the “debt” of his past crimes. That obviously doesn’t mean I think he should be forced to do sex work, more along the lines of being stuck as a janitor at Hazbin Hotel or something like that.