I'm not sure baseball can be held up as a model, given that the minor leagues are "minor" because they are under the boot of the MLB, due to the antitrust exemption [1]. Also, it's noteworthy that college baseball does exist and it goes deep into the summer. Pro basketball has an official minor league, the NBA D-League, but college basketball is still out of control.
[1] http://www.beyondtheboxscore.com/2008/12/3/678134/the-histor...