I do want to add that I know Gendry’s class issues have always been there, and it’s definitely been made even more apparent to him during the War of the Five Kings during his time in the wartorn Riverlands with Arya, so it’s not exactly that far-fetched that Gendry may become even more sensitive and/or bitter about it.
And I think it’s also worth mentioning that while Jaime sent Brienne out to save Sansa, Brienne spends her whole journey almost exclusively hearing news and following leads about Arya. So I think it’s a foreshadowing switcheroo. It’s also Arya who is legitimately trying to forget she was a Stark (Sansa isn’t trying to forget, she is only pretending to be Alayne to ensure her protection) and like I mentioned it’s Arya who had a blacksmith and future employee at an inn as companions for two novels. So while Jaime is referring to Sansa here I think we are meant to actually look at the reality behind this and reverse the foreshadowing back onto Arya, because it wasn’t Arya who was recently wed, that was Sansa. Also it’s Arya who is associated with a blacksmith (Gendry) and a fat-faced innkeep (Hot Pie). Now I know what you are going to say, that Jaime is referring to Sansa possibly marrying a blacksmith or innkeep, but if it weren’t for Jaime’s thought’s in the middle towards Brienne, you’d never guess which Stark daughter he is referring to because Sansa was only just recently married as well.