The Sioux City Journal says it will start in fiscal 2015, so the first likely will be 2015-16.
I am currently neutral on this change. Iowa is not on a torrid construction pace at the moment, so there will be fewer yearly changes. (This is different from Missouri, which is building a lot of new four-lanes and is just finishing a three-year 2010-12 map.) I don’t particularly like it, but I can understand it. If fewer maps are being picked up at the rest stops, it’s obvious to adjust accordingly.
The paper map still needs to exist. GPS devices are much harder to get “the big picture” on, not to mention reliance on batteries/electricity.