what do you think becomes of charlie after the story ends? why?

It is difficult to know for sure, but we are led to believe that he will actually end up more "retarded" and more mentally deficient than before. He may have feelings that he cannot understand and will not be even able to do what he could do in his past, at the time when the story began.

I think that after Charle leaves New York, he gets dumber and dumber, until finally he dies. Algernon died so why should Charle live just because he is a human.