Slanjaver, you make a fair point and if he does a 60minutes interview I will question his condition too.
However, it is common for athletes to suffer from depression upon retirement. Throw in his huge profile, a failed comeback, end of career, collapse of his business empire, a battle with his sexuality (I'm guessing) and having a history of depression, I would lean more towards it being genuine.
He has generally come across as a private person with his public life and I doubt it would be within him to play this all out publicly. However, i do see you point and i will question it if 60minutes are involved.