Should I get a double stroller

We’re planning baby #2 soon, we live in the city and don’t own a car. We currently have a compact stroller and it’s everything because I can lift it up and down the subways, doesn’t take up much space on the train, and I get to carry my little girl with me every where. When baby is born, she will be 2.5 years old and I’m just concerned about how much she will be willing to walk when we go out, nap time, if I were to get a single stroller. Any advice on this?