anything that helps reduce labor is an improvement. like the article says though, it needs to be replanted after four seasons (likely a drop in productivity as the roots and stems get too thick together and can no longer grow well - similar to strawberries).
in terms of crop rotations, you rarely will find single plants that do well in one location for extended periods of time. they extract certain portions of nutrients and then after several years they've depleted them, when such plants give a harvest that is removed (instead of left to rot and go back to the soil) then depletion is going to happen. there is no such thing as a free lunch - longer term you still have to rotate crops, manage nutrients and avoid poisoning the land.
upland rice varieties were a hot topic and probably still are because they require less water to grow.
wheat perennial varieties have existed for as long as i've been studying such things. they are similar to the rice in that they will produce but they won't produce a lot forever, so they need to be managed.
i don't know anything about perennial corn varieties.
anyways, the real interesting topics to me which are related are the ways that entire plant communities can co-exist and be really productive overall, but that is quite a way from monoculture of a perennial crop even if it is rice, corn or wheat. prairies are good examples of a complex ecosystem which works well for extended periods of time but then you also need the grazing herbivores that come through once in a while (but not too often).