Yup, wikipedia already maps all human knowledge. In fact , you don't need to map everything, just central concepts in every field. I think there's a law of diminishing returns - summaries of knowledge are extremely useful, but as you add more and more detail , there's less and less benefit.

I created 'Wikipedia-Prime', a series of 27 wiki-books mapping all central concepts in all fields of human knowledge. Approx. 16 700 articles was enough to capture all the central concepts used by experts in all fields.

Wikipedia-Prime Index: http://www.zarzuelazen.com/CoreKnowledgeDomains2.html