Can anything positive be seen/taken from the ending of A Streetcar Named Desire?

Concerning A Streetcar Named Desire,
the answer to your question depends on whether you're referring to the plot and the
fates of the characters, or to the play as a work of
art.

You might see the close of the play as positive for
Stanley.  His secret is safe.  He will get away with rape.  His life can continue as it
has.  Audiences certainly should not see this as positive,
though.

Other than that, I don't know that there's anything
else positive about the plot and the way the play comes out.  Blanche is on the way to
the mental hospital.  She has not been rescued, her sister doesn't believe her, and her
illusions have been destroyed.  A possible exception to this is that Blanche still hangs
on.  She is quite good at coping.  She views the conclusion as if she is being carted
off--rescued--by another gentlemen.  The play is certainly not predominately about
Blanche's perseverance, however.  She loses. 

As a work of
art, however, the conclusion of the play presents a realistic, modern or postmodern
ending.  It does not end happily.  Truth is often meaningless in our world, people get
away with crimes all of the time, and society is not an accepting and pretty place. 
Many stories do not end happily.  "Right" often does not come out
ahead. 

Not that there is anything virtuous or "right"
about Blanche.  She is messed up like all humans, as well as every other character in
the play.  This, too, elevates the play as a work of art.