Their 'knowledge engine' results have yet to show anything that's outwith their own purchased content or freely available open source content.
I think it's unhelpful in the discussion for people to blur the lines between organic SERPs, content ownership and the current form of their knowledge engine, as usually there's a personal agenda or a biased opinion behind it.
Sure, we can speculate "what google will do", "what they're trying to do", but until there's an instance of "someone elses content" being used in their knowledge engine, I don't see the correlation between it and 3rd party (copyrighted) content.
Some of the negativity that's pushed around about Google's SERP's is getting quite boring to be honest. Google is a tool to meet needs and nothing more.
Though the cynic in me says Google will use wiki and other content much in the same way it used DMOZ in its early days, a springboard to greater things.