Really, what would happen if it became a for profit product? Would I pay for access to the greatest single repository of information the world has ever seen? Or would I shrug my shoulder and let Google tell me that I actually meant to query something else, and trust that the top placed link is really the best?
See YouTube.
Wikipedia is already monetized, but not like most platforms:
How many times have you actually clicked the "donate" button when Jimmy Wales asks you to?
It's still interesting to note that the Wikimedia Foundation is getting more cash in donations than it requires to operate. If it wasn't a non-profit, it would actually turn out a profit.
Both of which are probably on the low end of what the content is worth.
When you really think about it, we write off free access to the largest repository of information ever as something which just happens to exist.