A Raisin in the Sun: Does this play have a "happy ending"? Why or why not? What do the Youngers have in store for them, once they move?

I would say that the ending is a relatively happy one.
Walter has stood up for his family, showing more commitment and veracity than he had
previously shown at any other time in the work.  At the same time, the family getting
out of its condition and moving to the suburbs is a move that is done out of the
family's best interests.  While there are so many social and personal circumstances that
are besieging the Younger family, it becomes redemptive to see them embrace the move
together and not show fear about.  The taking care of the plant, something that was a
challenge throughout the play, will now be facilitated much easier with this in mind. 
Additionally, I think that the expecting addition to the family also provides hope.
Certainly, they will face challenges in Clybourne Park and there is little to believe
that these elements will not be present.  Yet, the family is aware of that and still is
willing to take the risk for it is worth the reward.  This becomes the essence of what
immigration and movement in America is about, a reason for optimism at the end of the
play.