I think, as was said on that RPGnet thread, it's a matter of making this site more useful.
The various random generators are a good step, and getting them more functional, so that people are attracted to use the site - that'll lead to users contributing more.
The news articles are good too, because they catch things that are hard to find later.
That's also roughly why I started putting "Building This Character" sections on some of the character trope pages, to increase the utility of those pages. Ultimately, I'd guess the answer lies in making this site useful to more players. GMs already have a creative outlet for their thoughts and research - they put it into their campaign. People who mostly play instead of DM have just as cool ideas, but don't always have a place to express them.
Another thing we can do is authoring or compiling pages that are easier to use than it would be for someone else to do the research themselves. The fourth-dimensional lifeform page, if you don't mind me tooting my own horn here for a moment, includes a lot of information distilled from many sources. The information exists at other sites, but those sites don't really mess with the implications for 4-D life, and certainly not what it would be like to be hunted by a 4-D monster. Therefore, our coverage can save someone a lot of research and exrapolation. That's part of why I've been making so many scientific pages lately - because so many scientific sources are really dense, and even wikipedia's pages on science can be really hard to mine the applicable info from without melting your brain.
Eventually, we'll hit a Critical Mass, where there's enough content here it's just naturally self-sustaining. Just be patient, we'll get there.
