Well, there's no mean to "split" community, however, there definitely *are* people who don't speak french or english.
And it's no problem to switch between french/english(/german) wiki and forum if one wishes
Sometimes, it's just easier to use one's mother tongue.
Easier, yeah for sure, but interresting contributions (forum and wiki) will be split over X languages. ATM, we have two forums and two wikis and keeping those "synchronized" is already difficult (translation of the french wiki FAQ and other cool stuffs is planned), just imagine with X forums and wikis, it will be a nightmare. =p
But, translation of the official tutorials in others languages could be a good idea, for people who want to learn SFML but doesn't speak (actually read) neither English or French.
So good idea, but i think that splits the community over several different forum and wikis isn't really efficient. =)