If the atmosphere and functionality are to continue coping effectively with the ongoing growth, I think new ground will have to be broken in how to manage large online communities. The human brain only deals effectively with a community size of about 150 persons. More than that causes issues (strife). Most online communities only have somewhere in the neighborhood of 10% to 30% of members as "active users" to some degree. I don't remember the statistics as well as I used to, but I think (typically) about 20% are "regular" posters and another 10% are one-time or very rare posters. I have in the past found that this meant that a forum with more than about 700 members would be effectively bumping the ceiling on that 150 person "community" mark. What I have seen is that this tended to cause spin-offs in some fashion or another.
My thought is that older cultures tend to be more formal as a means to effectively cope with the larger-than-150 community size of developed cities. I don't know how to apply that to the culture of an online community but I think that is where there is hope for effectively coping with the size of HN. This is the largest forum I have ever participated in. I know there are some other large forums out there, but I don't know how they compare, size/traffic-wise, to HN. In terms of culture, my general understanding is they tend to be less polite.