Don't worry about the elephant!
Simple fact: only 10% of the original interest expressed in SE has materialized into sites, only half of those are intended to be public-facing (rather than internal/corporate) and only 10% of the public sites are going to endure on beyond the start of payments.
I have posted an analysis of the current meta.SE membership which, if you accept that signing up to meta.SE in the first place was an expression of interest, shows that only a minority of the less than 300 who were interested ever followed it up with any activity here.
Running a Web site is a big thing, much harder than it sounds, and running any sort of community site is ridiculously time-consuming. Everyone likes to fondly imagine that they have more time than they actually do. We all also suffer from the "Mythical Man-Month" problems of massively underestimating how long it will take to get a project off the ground.
The huge scythe hanging over SE sites in particular is the fact that we have a very limited amount of time to gain enough momentum to justify spending $129 every month. My guess is that the beta will officially end by Halloween and we will all exhaust our free month by the New Year. Many of us will try to give it a final push to drive membership, to ferret out the demand that we believe must be there, in the final weeks of the free month but, of course, the family and social demands of Christmas will slow us down and the New Year will see a massive drop off.
So, if you are truly determined to run a site on a particular subject, don't even think about that elephant, just fire ahead, seed, market and run your site as best you can, the competition will fall by the wayside one-by-one and you will probably inherit some of their users.
If you are serious about putting in the effort, and are realistic about the huge amount of time required, you will have a successful community regardless of subject. Just don't expect it to make money and remember that elephants like peanuts.