I'm a native speaking English person and primarily participate on the Unix and Linux site. I think as a business of providing a centralized resource for everyone in the world that wants to discuss subject X, creating many sites is counter productive, if you're truly trying to provide the best centralized resources.
I realize it's burdensome for people of the world to learn English, and it can be frustrating for these users too, so as is typically done in the computer and software industry, I say it would be more productive to try and create better tooling around translating the site into their native language where appropriate.
I've used google translate from time to time when I come across a non-English blog or site and it's worked reasonably well. Is it perfect? No, but based on the comments on many of the other answers, much can get lost in translation from one language to another.
By providing tools we could do the same thing with the translations as we do with the site, where members over time could refactor those translations through editing and commenting. Think of it as an additional view on top of the English backed content.
In this way if the viewers don't understand the translated version, they could always "view source" and see the actual content in English. It's a bit of a site within the site. It could be done using a few languages to start.
Creating these translations could be seeded with google translations to start, I would also limit to key questions to start.
Mixing in the data from which sites by top level domain visit could also be mixed in so as to only roll this feature out to questions that they frequent.
There are many directions to go with the above idea. But I'd much rather keep the pool of people as large as possible and not create competing silos of information than for no other reason than one group of people speaks X and another speaks Y.
Our power is our numbers and our different ideas we all bring to the table, and I for one would rather see a central solution that we all can participate in, rather than 100's of diluted sites where we all have to sift through looking for information.