Talk of a spinoff surfaced in September, just ahead of the release of the Iron Man 3 Blu-ray, which included as a bonus feature "Marvel One-Shot: Agent Carter," depicting Peggy Carter in her post-Captain America career with the Strategic Scientific Reserve (Atwell also has a cameo in Captain America: The Winter Soldier, which arrives April 4).
Soon after that initial report, Atwell acknowledged that she'd be interested in the TV project, saying, "The one-shot was so successful, the fanbase were like, ‘We want more of Peggy!' I think Marvel probably take that very seriously, and it’s certainly something I would be a part of doing. I’d be interested to show different sides of Peggy.”
The Mirror article offers nothing official, but instead quotes an anonymous source who said, "“Hayley is absolutely thrilled to have the opportunity and is incredibly grateful to Marvel fans who have basically been campaigning for a spin-off show for the past six months."