Just watched this, very interesting indeed...
But my opinion still remains that he committed suicide.
He was a junkie, very depressed, in lots of pain and hated his fame.
He just wanted to end it all.
The thought of suicide was always there in the back of his mind from a young age, he even attempted suicide in his teens and would have succeeded had the train not changed direction at the last minute. Those who have seen Montage of Heck know what i'm talking about.
It is highly unlikely that the SPD will open the case up, so lets just let him R.I.P and appreciate his legacy, his awesome music!