Apart from those few big names, there really are very few diasporic novels around. At least in the UK. I know, because I LOVE novels with non-European or North American characters and settings but I can hardly ever find them. There certainly isn't a special section for them; "multicultural" isn't yet a genre. They really are few and far between -- not at all proportional, it seems to me, to the actual demography. Perhaps it only seems that way to you? Or are you in the US, and it's different there?
I agree that those big names do get special mention when they produce a new book -- but not any more so than, say, Johnathan Franzen or Lionel Shriver.
However, I didn't want to derail.
I'm a shy person myself, which is why I read this thread, and I have to say, I am much happier doing online promotion than in real life. I used to HATE giving readings or interviews, actually going out there to talk to readers. I love writing to them. I have a bit of a speaking phobia. When someone says "let's chat on the phone" my heart sinks a bit; I'd much rather do it in writing.
On the other hand, I still can't get into the habit of running a blog or posting on Twitter. I really am not the chatty type.