I don't think we qualify as a new species because we can still reproduce with NTs and produce fertile offspring.
The closest thing I can think of that might describe the relationship between us and NTs is that we're a different "breed" of human... the difference between a Siamese and a Persian... They can still have kittens; they're still the same size, same intelligence (about) but they're definitely, recognizably, different--both in temperament and physical nature.
As for the different races of human being--black, white, Asian, whatever--there are enough differences there for classification; but they seem to be primarily physical and cultural-- mentally, the races are nowhere near as different as Aspie and NT. There are no two races that have such drastically different ways of thinking and relating to the world as, for example, me and my NT sister... and my sister and I were raised together, giving us the same cultural background--something different races don't have unless someone's adopted.
A black person and a white person are maybe about as different as a calico and a tabby cat--different coat patterns, maybe slightly different dispositions (calicos are said to be more assertive than tabbies)--but, at the bottom of it, both are just plain cats, one as good as the other (and both lovely, if you want my opinion, though I have more experience with tabbies).
But... when you get to Persian and Siamese... you get the body shape difference, the temperament differences, the coat, the energy level, the level of sociability, assertiveness, and the way they vocalize... That's the Aspie/NT barrier.
Different species? Nope. We're nowhere near that different from NTs. That'd be like saying we're bobcats and they're pumas or something... But whatever the human equivalent of "breed" is, that's us.