Sources report that Navajo, by far the most widely spoken Na-Dene language, dominates the family numerically, but none of the tertiary sources consulted totals Navajo together with the family remaining, more endangered members into a single Na-Dene figure.
What would resolve this A single aggregating source (a census bureau report or linguistic survey) that sums Navajo speakers with those of every other living Na-Dene language.
OpenNorth American indigenous linguisticsWikipedia: Na-Dene Languages