Agent Carter ran for a respectable two seasons, and it holds a pretty fierce cult following now. It never exploded in popularity, but for many who watched it, it holds a place in their hearts and the MCU equally.
There are chances we could see her in the future though. Hayley Atwell recently spoke to CBR about the character, and her possible future. While she admited it isn't up to her, and that she has let the character go for now, she is totally up for coming back. Specifically, she said:
I would be very happy to go back to her if she became available.
She also talked about how the character did grow old, so there is no real cap on when she could come back.
I hound [Marvel Studios co-president Louis] D'Esposito on a regular basis, saying, "Give me a movie!" I think the great thing about Peggy is, we know from "[Captain America: The] Winter Soldier" that she lives a long life, so she can come back. I'm banking on, when I'm in my fifties, I'm like, "This is the time. Let's see what Peggy's up to in this decade.
I am sure there is just a hint of joking in that last statement, but it's a good point. Atwell could come back for cameos pretty much into her 80s or 90s. That's probably making a few wild bets about the longevity of the MCU though, so lets settle on her being able to come back for as long as this train rolls. And why not? She is great.