In the 2E Planescape campaign setting, you didn't hear much about Cambions anymore, they started being called Tieflings. Which, I thought, OK, that's not a big change, because they probably call themselves by a different name than the humans afraid of being violated by demons call them.
In 3E you had a lot more of these progeny running around, only nobody called Tanar'ri by that name anymore, we went back to demons and the offspring were exclusively called Tieflings.
I'm given to understand that in 4E we don't talk much about the sexual habits of greater and lesser demons, and the Tiefling is now a true breeding race of its very own...I guess because horns and tails are cool.
Anyway, this sort of thing really messes with the long term gamer's continuity. By design, of course, because long term gamers already own most of the stuff they need and unless you destroy their continuity and stop supporting their products, they won't buy the new stuff. I actually do still buy the new stuff, and not just to complain about it being new, though I am going up in levels in my grumpy old guy character class.
In any event, here is how I handled the fact that I have several cambions on my miniature shelf, monstrous compendium sheets for them, and a rapidly growing pile of tieflings.
The following is a blend of my ecology description and the 2E entry for Tieflings from the Planescape boxed set. Let me know if you think it is plausible.
"Tieflings are the offspring of the planes, as varied as the places they call home. They are similar to Cambions, in that they have Tanar’ri blood in their veins, but these are the children of Cambions and other races, a kind of demonic quadroon. Where Cambions are universally male offspring, tieflings may be of either gender and they are able to breed more tieflings by mating with humans, demi-humans, or even among themselves, which they have begun to do in ever greater numbers as they tend to be shunned by those not of their own kind. Some scholars believe that the tieflings are well on their way to becoming a truly separate race. One thing is known, they are proliferating and becoming as frequent a sight in some larger cities as elves. Superficially human, their appearance always betrays them: some sport small horns, other have pointed ears, scales, a cloven hoof, or just a wicked gleam in their eye that never leaves. What they all have in common is a quick temper and a chip on their shoulder."