Maybe it's me,
but I think that we are missing the real, huge point: *we are not ready for this*.
I mean, we, as a community: in the few days in Vienna, we discovered how many problems each Wikisource and community has, and that was the first time we had the chance to meet and talk (at that scale).
Yes, being all in the same place would maybe shorten the distance within the international community, but it would be an enormous challenge for the amount of software tweakings (gadgets, css, proofread page, layouts, everything), and it would be a real, literal "babel" of languages.