Not an important issue. Corn ethanol will eventually be phased out because there is no real upside to it any more. Plenty of oil being produced now.
The BIG solution is to find some other use for the excess corn being grown by our super-duper efficient farmers.
Excess corn not a problem. Before the ethanol boom, corn acres had been dropping for decades.
Plenty of room for more acres in hay, wheat, cotton, rice, etc.
Iowa farming would be little affected. Corn is a natural, a tall grass on what was tall grass prairie. Biggest change will be outside of the prime Corn Belt.