This is like asking how fungible are calories. People with the means to mill and cook with wheat flour can probably manage with corn too if the alternative is starvation.
I don't mean on the consumption side. I mean on the production side. Do they grow in the same soil? Do they take the same nutrients? Do they have the same water / sunlight / temperature band tolerances?
Looks like that rotation is pretty common but there are some details to concern oneself with.
Much of it boils down to water and/or irrigation. Maize (corn) likes wetter, wheat can stand dryer. In the US the corn belt starts in Ohio and includes eastern Nebraska, wheat is grown largely on the far western plains.
Wheat is also a viable winter crop --- fall planting / spring harvest for "winter wheat". That typically means 2 crops a year (winter + summer), and possibly more.
Rice is the third staple crop, though it wants a lot of water, and tends to be grown in subtropical climates as with China and India.
Other substitutes include barley, oats, millet, etc., though those are far less prevelant than wheat & maize.
