The number attached to this structure in popular writing comes from Andres de Tapia, who came to Mexico with Cortes and put the skull rack at 136,000. It is worth being exact about what that figure is. It is a number in a narrative written by a participant in the conquest, in a genre whose business was to account for what the campaign had done and why it had been right. Modern scholarship does not treat it as a count of anything.
What the excavation offers instead is a partial exposure. The structure runs beneath standing colonial buildings, and the archaeologists work in the space the city leaves them. The published counts, which are in the hundreds, are counts of the portion that has been reached, and they have risen with each season of work. Nobody has proposed a total for the whole structure, because nobody can see the whole structure.
That is a genuine gap rather than a disagreement, and it is recorded here as one. There is no scholarly camp arguing for a figure against another camp arguing for a different figure; there is an incomplete excavation and an honest silence. What would close it is full exposure of the structure, which would require access under the buildings above it, and a minimum-number-of-individuals count taken across the complete assemblage rather than across the reachable part of it. Until then the correct answer to how many people are in the great skull rack of Tenochtitlan is that it is not known.