I see the question-asking rate at this site has dropped to 0.4/day. It seems like that alone could threaten the future of the beta, even if there are high quality questions and all the tag and translation issues are sorted out. Is there anything we do to encourage more questions? Is it time to try some "weekly topic challenges" to flesh out the site?
I wonder if a good way to encourage Spanish questions would be to do a weekly or monthly campaign around a piece of work written in Spanish. That is, we could encourage questions about a particular Spanish-language novel, author, web site, or literary genre.
This would encourage people to read something in that particular area, then ask questions to understand what it's saying.
This might be particularly valuable if the selected piece is less contemporary and uses more obscure language constructs.
It would also be easier to participate if the resource was available online for free. So maybe some Spanish classics with expired copyrights.
Don Qujote de la Mancha might be one example. And it's such a vast work, perhaps the weekly campaign could focus on one chapter at a time, rather than the entire piece of literature.
SE has offered real prizes for some sites, but AFAIK, those are all sites out of the beta stage. We might have to be content offering an "Honorable mention" as the prize of the week for now.