Well, it's something we'll never know, but when push comes to shove, I'd take 'good atmosphere' over being taken seriously in the mainstream and raising the profile of the Hugos any day. Considering that about 60% of the top-grossing films of all time fall within sf/f, there's an entire tv station devoted to it, several of the most popular tv series of the last 10 years have been sf/f, and re-runs of older series are a staple in both the US and the UK, and that's not even counting comics and MMORPGs ... how much more mainstream can the genre be?

And fandom? I'm sorry, but how could it possibly matter what people think? People willing enough to spend time and money on the accoutrements of fandom are no more (or less) mainstream than any other group of people who spend a lot of time and money on any hobby, whether it's LARPing the Civil War or diving or collecting spoons. It's a first-world problem.