Maximum contributor count?
Once the incubator is fully functional, how many contributors per language on average will be there?
How many hours of work will a course approximately take to be developed to beta? I hope it will be less than a month.
Luis once said the optimal number of contributors should be 5-8, but that could change. Of course we have to take in account that more contributors doesn't mean faster development or better quality of a course (primarily because more contributors means more opportunity for disagreement and more difficult communication).
As they are working on their courses current moderators and contributors are providing feedback to Duolingo team so that incubator can be tweaked and bugs can be corrected.
English for speakers of Russian language is currently at 30 % (words+interface) after 13 days. At this pace they could finish it in 3-4 weeks, but we have to take in account that they will have to test it before promoting it to beta stage (I don't know how long does it usually take for that).
My rough estimate would be 1,5-2 months for an English course to graduate from phase 1, but I hope it will be a bit less than that. :)
I hope it will be more than a month. Language learning takes time, developing a course takes time, unless either the quality is low, or the creators are expert translators and educators. This is particularly true if there are new languages being added.
Think of Mandarin Chinese or Arabic for example, arabic is read from right to left, Mandarin is read in another direction(can't recall exactly). There are also issues of choosing simple sentences to teach, how will we write the Chinese/ arabic characters(for those who don't have a chinese/arabic keyboard), creating new modules to explain concepts that don't exist in the original language, and so on.
Regarding the maximum contributor count, I think Prof Luis is always dodging the question, he indicated that 5-8 is optimal, although he didn't say that is the maximum. I think the contributor count can be hundreds once the course reaches beta is released, since mainly they will just be suggesting, and translating new content which the moderators then proofread and add to the relevant skill/section.
Also, I'm not sure if you are referring to contributors(moderators + helpers), or just contributors. If you're referring to the latter, then it is 5-8 . Otherwise, according to Prof Luis it is 3 moderators at most, and an unknown(5 maybe) number of helpers.