Hayley Atwell will reportedly reprise the role of Agent Carter in Agents of SHIELD season 7. Actress Hayley Atwell has jokingly referred to the role of Peggy Carter as the gift that keeps giving. She originally signed up for a single movie. However, she's now played the role in four films, starred in her own MCU TV show, appeared in flashbacks in Agents of SHIELD, and voiced the character for Marvel Animation.
The Agent Carter TV show ran for two seasons, from 2013 to 2014. Although it had a devoted fanbase, Agent Carter was canceled by ABC because the network wanted to put Atwell in something a bit more mainstream. The abrupt cancellation meant that viewers never got to see Peggy Carter actually found SHIELD, the event the show had been building up to since its inception. Worse still, the show ended on something of a cliffhanger, with a major character death.
According to FandomWire, Atwell will be reprising the role of Agent Carter once again in Agents of SHIELD season 7. The Agents of SHIELD season 6 finale ended with Mack and his team traveling to the past, sometime around 1930 or 1931, when the Empire State Building was still under construction. That's still the wrong time period to encounter Peggy Carter - she'd be around 10 years old in 1930 - but FandomWire speculate that there'll be more time travel.
It's important to treat this report with a degree of caution, as FandomWire hasn't always proven to be a reliable source. Their reputation is improving, however, particularly after they proved right about Black Lightning's "Crisis on Infinite Earths" appearance. Furthermore, there's already circumstantial evidence to support the idea that Peggy Carter could be appearing in Agents of SHIELD season 7. SHIELD actress Ming-Na Wen unwittingly name-checked Enver Gjokaj, a member of Agent Carter's supporting cast, in an Instagram post; she swiftly deleted the post when eagle-eyed fans spotted the name.
It's not hard to imagine what role Peggy Carter could play in Agents of SHIELD season 7. Fitz and Simmons are essentially leading a sort of "Time War" against an alien race known as the Chronicoms, who also possess time travel technology. The android race aim to rewrite the past in order to ensure SHIELD cannot be a threat to their plans for Earth in the present. Logically, that means they're likely to target key SHIELD personnel. Peggy Carter, one of the founders of SHIELD and a long-serving director, would logically number among their first targets. Meanwhile, this kind of plot would allow Marvel to tie together loose plot threads that are four or even five years old, finally showing Agent Carter take charge of the fledgling espionage agency.