I'm doing some research for the Conscious Choice article on Chicago as the Greenest City, and have found that the plan to modernize O'Hare doesn't include anything about high-speed rail, or even anything that ensures that the new airport will take advantage of existing rail connections.
Here's the part of the Master Plan that discusses rail and public transit.
We can do much better. O'Hare and Midway should be connected up to a high-speed rail system, just as Newark Airport is. It's ridiculous that O'Hare is jammed up with flights to Champaign, Springfield, Milwaukee, Madison and lots of other nearby cities that are better served with rail, not air.