Dungeons & Dragons does not exactly have the best track record when it comes to translating critters from real-world mythology into the game, so it does not bother me much if the succubus ends up being a devil, demon, or something else entirely. What does bug me is when someone argues that it should be a demon "because that is what is was before" and/or that the wikipedia article cites it as a demon.
In regards to the first argument I was one of those who preferred them as devils, both because a Lawful alignment seemed better suited for a being trying to use deceit and subterfuge to corrupt a soul, and devils in general had a strong theme of corruption (as opposed to Chaotic demons,
who favored the route of destruction).
Additionally I am of the opinion that repeating material from past editions just for the sake of repeating it is a terrible idea. This is why we have attacks and some spells determining success in different ways (except for magic missile, which is the only spell that automatically hits), a heavy reliance on magical healing, rigid classes, magic systems that make no sense at all, per-day resources, angels that just look like winged humans with different skin colors, curses with benefits, and more.
As for the second one, why stop there? Previous depictions of the succubus described them as monstrous rather than attractive, but even later representations made it so that close inspection could reveal features like bird-like claws or tails. They would also collect semen from men, then an incubus would use it to impregnate women, though I am not sure if they just give it to an incubus or change their gender. Interestingly the Arabian version could only be seen by certain people, and even then they would just see a cat, dog, or similar animal.
All of this sounds a lot more interesting than a woman wearing a devil costume that can make out with you and use a souped-up version of charm person as a spell-like ability. I would make them monstrous (or at least be unable to hide specific features), gender neutral (but able to change their shape and/or gender), and also tack on illusions so that they could at least pretend to give creatures whatever the desire most. It would also be cool to have a variant power set that would render them invisible to most people, or make them just see an animal.
But we will most certainly get a succubus that is female and sexy and will totally make out with you because that is how it was before.
I am also not too keen on the idea of making cambions specific to succubi. I get that that is how it works in mythology, but where does that leave tieflings, who will apparently have randomized physical traits? Are we going to have a unique name for each kind of half-fiend? Is there any reason that draegloths are specific to Lolth, or that durzagon are the result of an infernal bargain? Why not just make a set of half-fiend powers for each type of fiend that Dungeon Masters can attach and justify as they see fit?
That sounds a lot better and more useful than books filled with arbitrary race-fiend-flavor combinations.