ESPN has no interest in replacing the NCAA because they cover ALL sports, college and professional. Why would ESPN want to spend all the time and effort to run an entire amatuer based division of sports made up of 18-24 year olds? Money? Sure but then they have to pay all the administrators to run it, ESPN would have to handle very single aspect and where does the additional income come from?
They make too much money now, replacing the NCAA would cost way too much and be a huge hassle. Plus then the other professional leagues could come together and start their own networks, would simple by merging all the leagues together. Ok not simple but just as easy as ESPN replacing the NCAA.
NCAA being replaced by ESPN makes no sense.