First the question would be to understand if the understanding of the product is correct . Wikipedia is a free community sourced encyclopedia that offers all information under the sun. Apart from that it offers free books, travel guides as well as course materials. But for the scope of this question, I am assuming we are restricted to the encyclopedia .
Understanding the users and pain points.
1 . Researchers who are writing a paper or researching a topic .
2. Students who need help with an assignment or homework
3. Teachers who prepare lesson plans
4. Casual users who wish to find out about a topic .
5. People who are passionate about certain topics or communities like sports lovers, entertainment buffs, etc
1. Since it's community sourced, the article might be factually incorrect .
2. Instead of information on a topic, might need help with an answer or verification of a fellow researcher.
Probable Revenue Sources:
1. Expert Series: Engaging key influencers to write content on a topic on a subscription basis .
2 . Answer a question: Get credits for answering a question or buy for getting it answered .
3. Research paper services: Take help of fellow researchers on giving you feedback on a paper .
I think of the three, the first one is the best on, as for others you have alternatives in place.