Why should and and all content be stored in a special place called "wikipedia" or some other name, when you can write anything you want about any subject on your blog and have it indexed by a central search engine?
Wikipedia offers two things that lone blog posts don't: collaborative editing and "findability" (SEO).
Findability should be the problem of search engines; the fact that we need to go to Wikipedia (or IMDB...) to find specific information is a testament to Google's imperfection.
If you want to publish "a 10,000 words biography of [your] cat", you should do so on your blog, and that should be easy to find when searching for "hugh3's cat" (but not when searching for "cats", unless you're some modern-day Montaigne who can teach us eternal truths about cats just by speaking about his own).
I would even argue that Wikipedia hurts findability to some extent, since it relies on anonymous editing, and reputation builds on identity. Knowing who wrote what is a very useful piece of information (something Quora is addressing).
What about collaborative editing? Successful collaborative editing is made of two parts: software and a community. The software problem is largely solved; a working community of people who know and care, is the hard part. But it's also in the process of being solved by what StackExchange is doing: building sites around existing communities.
So here's what I think will eventually happen:
- human-machine interface / findability engine: Google
- clusters of (constantly updated) information: StackExchange sites (and others)
- niche content: your blog
In this future I'm not sure there's much room for Wikipedia; Wikipedia was built around the idea that there is such a thing as "static" knowledge or "eternal truth". There isn't: knowledge is a process and a conversation.
(Wikipedia is in fact a kind of cache for the current state of knowledge, but that problem could probably be solved differently and more efficiently.)