"Species" is a vague and slightly philosophical concept, but I think an actual population of people with 44 chromosomes would have to become established before the term was applied.
"A species" is typically defined as something like "a group of individuals that can breed with each other".
So if we discovered the last Tasmanian Tiger out in the wild somewhere then it wouldn't count as a species any more because it's the last one and... aww, this is too nitpicky a semantic debate even for me.
The definition is obviously about potential: the last healthy Tasmanian Tiger could mate with another healthy Tasmanian Tiger and have baby Tasmanian Tigers.
A healthy mule can't mate with another healthy mule and have baby mules.
People who happen to be sterile or decided not to have kids can remain a part of the human species...
Of course they would have the same genes as other humans, just distributed on less chromosomes. For all practical matters, they would be indistinguishable from 46-chromosome humans.
