"Are we at risk?"
Regarding the question of whether we are "at risk of getting switched off at the end of the public beta period", the following blog post is a good read:
When will my site graduate?
The most relevant excerpt is (emphasis mine):
How long can a site stay in beta?
The simple answer is, it takes as long as it takes. We’ll wait. If a site needs more activity, go out and evangelize it. As long as your site shows steady progress and continues to make the Internet a better place to get expert answers to your questions, it will march on. We don’t want to kill a site because it hasn’t reached full status in 90 days. Nor do we want to set a hard 90-day limit and launch a site too soon.
There’s more to the health of a Stack Exchange site than having a lot of questions and answers. There’s an economy to the site with reputation as its currency, and voting drives that economy. A site absolutely needs on-going, sustained voting to build a class of leaders that help run and govern the site. Without leadership, there can be no community.
So from this point forward, the graduation date of a site will depend heavily on having enough users with sufficient reputation to properly lead and govern the site. It's much more important to graduate a site when it has become self-sustaining, and has established a healthy community of avid users, closers, and editors — rather than imposing an arbitrary 90-day limit.
Thus, the order of launch will favor those beta sites which have achieved the most "excellent" ratings on our Area 51 stats panel. For everyone else — keep going!
Based on this, I don't think we need to actively worry that we are going to get shut down at 90 days. Like you said, we're only on day 28, and to me our stats look pretty good -- Especially when I look at stats of other sites that are currently in beta. Some of them have been in beta for a long time, but their stats look worse than ours.
"Should more be done?"
Of course, the fact that we seem to be doing OK right now does not mean we should become complacent. Luckily, the text above gives some good pointers about what we can do to make sure we keep up the pace and get closer to a full launch:
Vote. Looking at the list of questions, there are many posts that get decent numbers of views. Yet, the number of people exercising their right to vote on them is a lot smaller. So, if you take the time to click on a post and read it, vote - even if it doesn't address a problem you are currently facing.
Talk about the site. Tweet links to posts that you find interesting. Talk about the site on your blog. Put it in your Facebook status that you have been spending way too much time reading questions and answers on here.
Area 51 metrics explained
Information about how to interpret the different statistics shown on our Area 51 page can be found here:
Does this site have a chance of succeeding?