1) It's a process. We already have non-white people in top positions (both in the industry and in academia), so there's no lack of inspiration, but it takes time for those who have inspired to make their way through school and immigration. Right now there are multitudes of Indian and Chinese students in American universities: in a few years you'll see them at conferences. And that is already going to happen: they're certainly not going to drop out of their degrees and go home because some Brits were not diverse enough with their conference in Manchester.
2) From what I've seen, many of those students are more interested in enterprise or research applications than in doing web development with Ruby, so you might see them at slightly different conferences.
3) This particular conference was in the UK, not in America or in India or in China or in France. Let's be careful not to call the entire country racist just because it's mostly populated by whites.