"Every single person on the planet" is a bit of rhetoric, but a serious bit of rhetoric. I will feel that this mission is complete if we have an encyclopedia written in enough languages so that 99.99% of all people _who are able to read in some language_ can read a Wikipedia.
African language Wikipedias aren't very useful for this goal. Most Africans who are able to read are able to read in some colonial language (fr, en, pt, es, ar). In Bamako you have to look hard to find books, papers, or anything written not in French...
I think actually that the mission is complete if people who are not able to read in some language are included. By using text-to-speech synths and voice recognition anybody who can either read or hear could access Wikipedia. Otherwise some 80% of Mali's population is excluded from the mission.
The fact that there is more information available in people's mother tongue will be an incentive to actually learn to read (and write) in that language. But the same would count for Zeelandic or Limburgish, actually. The difference is the literacy rate and the (dis)similarity between the written and non-written languages.