I thought about it actually prior to the ruling, because it’s been legal in New York for a while. But I think the thing is, Steve and Tony haven’t actually been together a super long time – they dated just long enough for Steve to really get in deep, then Tony was kidnapped, then they lived together but on the understanding it was both temporary and recuperative, and then it wasn’t that long after they got back to New York that Tony started dying and Steve got sent to New Mexico.
So I think – their relationship has withstood a lot, but they still need some time to rebuild trust, between Steve lying about his job earlier and Tony lying about his terminal heavy metal poisoning recently. So I intended (still do intend) to frame the events of Avengers as the thing that really allows them to stabilize their relationship. They’ll get there eventually, but right now Tony’s too emotionally stunted to propose and Steve’s too smart to say yes if asked.
Sam and Bucky, on the other hand, have been together since before Steve and Tony met, and they’ve been living together since Steve and Tony started dating. And while Sam doesn’t want to pressure Bucky, Bucky is particularly incapable of direct action when feelings are involved.
So I figure Sam probably just like, wakes up with a fucking ring on his finger one morning and is like “The hell is this” and Bucky brings him breakfast and there happens to be a wedding invitation on the tray, which is how Sam was VERY CORDIALLY invited to his own damn wedding.
Steve is obvs Bucky’s best man. I think Sam gets Peggy to be his, but she only agrees on condition she can go in full tuxedo drag.