Actually here in Toronto there is a large gay population and I have noticed that there are many more gay couples consisting of Asian and white males these days. Of course it's hard to say who the 'female' is in that regard, or whether such a dynamic even exists, but I have noticed it. (It's hard not to notice two dudes holding hands, not that I find anything wrong with it) But within that community, as far as 'street-visibility' goes, I notice it much more these days as opposed to when I was in highschool.
In general I think that whatever cultural or racial barriers were preventing this co-mingling from openly happening are really starting to come down as I've also seen many more white females with Asian males in recent years. I'm half-Japanese, but up until my recent trip to Japan I only dated white females. I was never against dating anyone else, it was just that way because I was socialized in a caucasian environment at school, had mainly caucasian friends, and liked caucasian women primarily. I never really thought too heavily about it though and didn't experience any problems, perhaps because I don't look stereotypically 'Asian' and I speak fluent English. But I do remember one conversation with an ex and she basically said that I was different (for those reasons) and that she wouldn't be naturally inclined to date an Asian male.
These barriers are being challenged in movies too though. In Jet Li's 'Unleashed' a tangible love interest scenario develops between the main actress, a white female, and Jet Li. I don't remember if they kiss but it was certainly a strong representation and rare in major cinema. It took a long time for interracial couples of black and white to become 'acceptable' in the mass media, I think the same changes are taking place now with Asian males and non-Asian females. I would imagine that other 'pioneers' in this regard would be Bruce Lee and his wife Linda Lee Cadwell, and regarding white men and Asian females, John Lennon and Yoko were obviously a strong icon in mass media.