I'm concerned that LEGO.SE may be at threat from any future site cull
Well, yes it is! In fact, as of last Friday morning, it was on my list to close. The activity has fallen off precipitously, to the point where the stats are worse than many of the sites that are being closed.
It's not closed right now because I wanted to try something, as sort of a precursor experiment to some changes we're planning for the site creation process. LEGO made a good candidate for this because it's a fairly accessible yet extremely niche topic, there's not much in the way of controversy here, and the community has shown themselves in the past to be fairly active in dealing with perceived issues - as evidenced by you posting this thread soon after the blog post went up (and long before I was ready with my planned post!)
So what's gonna happen?
Well, it'd be awesome if you somehow managed to bring in a bunch of new users and get this place hoppin'... But frankly, I don't really expect that given the trends. My current impression of the site is that we've simply tapped out the interest among the current SE audience.
So the experiment is simply: can you maintain what's already here? The one good stat on the Area 51 page right now is the 99% answered questions. I'm not seeing any spam, or obvious broken windows. If it stays that way - if there are a few of you willing to keep the lights on and the lawn mowed - then fine. We'll have a tiny little site for LEGOs tucked away.
If I come back in a month and the windows are smashed in and weeds are growing everywhere, then it gets closed, just like that.
Like I said, it's an experiment. It might go "boom".