I also like that plot idea of Bucky being the triggerman on Stark's parents... but the TV series has so far carefully avoided being plot-critical to the movieverse (even to the point of stealthily defying them, via both Coulson and SHIELD still being around in new forms, despite both being officially gone in the movies), and I'm not sure I'd want them to break that by having Bucky first revealed as the killer on the series, even if it is reintroduced later in Civil War.
If they do have Miss America and Whizzer, they'll probably have to be QS/SW's grandparents or great-grandparents rather than parents, since the twins are barely out of their teens in the present day in the MCU (according to Marvel/Whedon, the whole reason QS and SW are showing up in Age of Ultron is to add some younger blood to the team[footnote]I'm speculating another purpose, though. Whedon has said that one of the main thematic goals of Age of Ultron is to confront and deconstruct the reactionary/quasi-fascist aspect of the whole superhero genre, basically furthering the conversation that Winter Soldier started. So I'm predicting the twins will join Team Ultron primarily to give the socially-conscious-and-thusly-angry-at-the-world Millennial audience some characters to identify with. Given how many comic/movie fans (including Bob) are of the "Magneto was right" school of thought, I imagine it'll be pretty appealing to picture myself as one of the chosen few standing by Ultron's side as he overthrows the kyriarchy and destroys our cruel and savage kin. Heck, given that Winter Soldier was all about how outrage at the current state of things is perfectly legitimate, maybe the debate about whether The Villain Has A Point will be another seed of the conflict between Cap and Iron Man?[/footnote]). Golden Girl could probably stay as Thunderbolt's aunt, though, obviously.