Complex sentence: The criterion of whether an encyclopedic article is possible should be the gauge--if a new field of social or cultural study emerges in the future and lends itself to an encyclopedic article, the related categories will then become valid even if they have previously been deleted.
Split into simpler sentences: The criterion of whether an encyclopedic article is possible should be the gauge. If a new field of social or cultural study emerges in the future and lends itself to an encyclopedic article, the related categories will then become valid even if they have previously been deleted.