The canon says no such thing. It says the only known queen was killed by the Chosen One. It does say they are dying out, but long lived, so they can quite feasibly be in New Vegas. Also, as they are a manufactured lifeform, I can see lots of ways to reintroduce them as a major species again.
But by that logic a Super Mutant from the West Coast COULD become a behemoth as we dont know how old a behemoth has to be to reach that size, So if a super mutant is over 100 some odd years old since its dipping, it COULD become a behemoth as faras we know.
And B. My point is this,both what you said and what I said would just be cheap fan service if they just randomly reintroduce these creatures.