I doubt he'll play in Brazil and there is not point playing there anyways. tennis and Olympics don't really agree with me. However, he is still doing very well and he loves tennis. at 31yo he is pretty much destroying anybody not called Nole, Rafa or Murray. I think as long as there is some passion left, he should keep playing. Fed is one in a million, tennis needs him. My feeling is he'll play probably next 2 years and then retire but who knows? I also think he'll slow down, playing less tournaments but he's been always smart with his schedule.
as for the place of retirement Wimbledon would be appropriate IMO.