It's now accepted that he didn't. In truth, such hypothesis was clearly ludicrous from the start, to anyone with half a brain; it was kept dangling just to distract the public, trying to paint it as "just another homo killed by his own weird fetish".
Either this was a cold-war style assassination, or the guy brought home a stranger too many; we'll likely never know the truth about it anyway.
I don't know if you have any information not in the Wikipedia article but I don't see anything there suggesting suicide was ever considered as a possibility. All is see is the police and coroner saying he was murdered but they don't know who did it.
http://en.wikipedia.org/wiki/Death_of_Gareth_Williams