This topic seems a bit like walking on eggshells, especially since their are some very adamant opinions out there. My experience is that translation is somewhat of a losing battle, but may still be well worth the trouble, especially when trying to reach certain communities. In an ideal scenario translation responsibilities fall back on people within the community (rather than assuming responsibility centrally in a project).
Way back when the digitalhumanities.org site was launched we created translations in French and Italian – both were done with modest stipends. The site then was powered by a wiki and there was a mechanism to notify editors when a change was made to a translation page, but over time the translated content fell out of sync. That was using TWiki – I'd be curious to see if MediaWiki has more sophisticated support, but I suspect not (several Wikipedia pages are not translations at all, but entirely autonomous articles).
For other projects I've built custom localization modules, partly because I find it easier to keep all translations together in a common resource (as opposed to one file per set of language strings). But that approach doesn't scale and only works in a small development team.
I guess for most of the multilingual projects I've been involved in the translations seem like a gesture more than a necessity, and frankly I'm not entirely convinced that the gesture has been worth the trouble. It's like the DH conference call for proposals that exists in several languages, which is a worthy nod to multiculturalism, but ultimately it's unlikely that someone would propose something without having functional reading competencies in English.
It may not be a choice in your case, but a generic piece of advice would be to do translation on a concrete need basis only, not on an anticipated need basis (this might be akin to agile programming where a client expresses a need rather than the developer anticipating a use). If translation is in the cards, then hopefully there's an engaged group of people who can sustain it and avoid linguistic atrophy over time.
<annotation>hope I'm not sounding cynical</annotation>
<annotation>this probably didn't even answer your question</annotation>