Is there a way for labels to be displayed in KML only when zoomed in (or out) beyond a certain scale range, just as it is possible in ArcMap?
If exporting to KML from ArcGIS, I guess the first step is to label the features before exporting.
I think the closest thing to scale dependent layers in KML is Regions.
However, Layer To KML does not write them and I do not think they would support the concept of scale dependent labels. There is a document on KML support in ArcGIS that mentions that regions are not written.
Examples of KML items not supported in exported KML files include COLLADA, regions, and time spans (animations).