I'd love to have the classic purple suit. That said, if the realism is taken to extremes (as in, a psycho can't wear a purple suit), I think the hat and trenchcoat would be a splendid way to keep it a bit more toned down but still look like the Joker. Even as I type this though, I cringe at the concept of having to tone it down so as not to have the classic Joker costume. It just seems so unnecessary. I really don't see any reason why they won't have him wear it, as I think about it.
But I would like him to have both.