The ending to the play shows how the Younger family will strive for their dream regardless of the many factors that dispel them from doing so. The Karl Lindners of the world, the neighbors who doubt them, as well as the social conditions that challenge families like the Youngers as well as the personal demons that have gripped Walter and other members of the family were overcome in the final scene. At this particular moment, the ability to be able to establish a better life for one's family is valued above all. This makes the overall ending of the play a positive one, but one that is filled with challenge. It is almost as if Hansberry is indicating that while there is hope for the future, there will always be struggle and challenge inherent within it.
At the end of the play, after Walter has stood up as a "man," the family packs up the apartment and moves. In the very last scene, Mama takes a look around the apartment, grabs her symbolic plant and exits. Her last actions demonstrate that she is saying farewell to a place where she helped her children (and her plant) grow so that all of them can move on to a place with more "sunshine" and room for them to grow more.
The significance of the ending of A Raisin in the Sun is that in many ways it becomes a reaffirmation of the family's traditional pride.
The crisis of the play occurs when Walter loses the insurance money inherited from his father because he allows himself to be duped by Willy Harris who has run off with both Walter's and his sister's shares. Knowing how he has disappointed his mother, Walter is so ridden by guilt, disillusion, and self-disgust that he decides to phone Mr. Lindner. Having reached the nadir of his life, Walter tells this representative of the residents of Clybourne Park that his family will take the money offered them to not move into the new neighborhood.
But, when Walter informs his family that he has phoned Mr. Lindner and told him that his family will take the pay-off money, Mama speaks,
MAMA: Yes—death done come in this here house. (She is nodding, slowly, reflectively.) Done come walking in my house on the lips of my children.
Beneatha declares that Walter Lee is no brother of hers, and, hearing this, Mama chastises her for saying such words. Beneatha reminds her mother that she taught her children to have some pride. Mama then reminds her:
MAMA: But, I thought I taught you something else too ... I thought I taught you to love him.
Soon, Mr. Lindner arrives, and Walter emerges from the bedroom. He falters, but he tries to explain to Mr. Lindner that his family has phoned him to let him know something. He tells this representative for Clybourne Park that his father nearly beat a man to death for having called him a bad name and insulted him.
WALTER: I mean—we are very proud people. And that's my sister over there and she's going to be a doctor—and we are very proud....And we have decided to move into our house because my father—my father—he earned it for us brick by brick.
A nervous Mr. Lindner then tries to appeal to Lena, but she merely tells him that he has heard her son, and they are moving. She adds that there is nothing left for her to say about the matter.
After Beneatha steps outside, Mama speaks to Ruth woman-to-woman about her son, who has already gone out:
MAMA: He finally come into his manhood today, didn't he? Kind of like a rainbow after the rain.
RUTH (biting her lip lest her own pride explode in front of Mama): Yes, Lena.
Significantly, the family is again intact, and Walter Lee has regained some dignity. Most importantly, he has put aside his pipe-dreams, and he has reaffirmed the values of his family and his responsibilities to them. Now, the family is reunited and is whole again.