No no, he's right, I meant both, betrayed and snow elves alike.
Because it was 4000 years ago for the betrayed as well, even if the effects are still being felt today. The actual atrocities were commited thousands of years ago by people who are long dead, so who would they take revenge on? Innocent men, women and children? The Nord who inhabit skyrim now can not turn back time. They can not change what their ancestors did. They could try to make up for it and give the betrayed back some land but really, they had nothing to do with it.
And also, the only effects still being felt today are the effects of the toxin. None of the betrayed who live today have lost family or friends to the Nord for example and the dwemer...well...getting revenge on them might prove difficult.
I'm not saying the Falmer would succeed in revenge, only that a bulk of them would probably try.
I know the Nords now can't fix what has been done, and I do understand that those who commited the acts are long gone, on both sides. Revenge usually doesn't involve much logic, though. The Falmer are growing though. With all the gold they seem to have on them, I'd even go so far as to say the larger setlements might even have a currency system in place. An organized religion of some form might not be to far off either.
What I'm saying, is that as they grow, they're culture will develope. They'll evolve, and gain a sense for themselves as a people. A real, solid, culture. And they'll start asking questions, like is there a a way to better their lives, what is up on the surface world, and why are they bellow? And at that time, I don't think Gelebor could keep the truth from them any longer.
They'll learn about their past, and quite a few of them will feel, well, betrayed. Their entire culture would be built on a lie, and they're not who they think they are. That would be ... well, horrible. It would be as if the Falmer, even though they would be only learning of the betrayal thousands of years ago, were being betrayed again. Some of them might be able to come to terms with that, but I would venture that the bulk of Falmer would want answers. And with no answers to be found for such a situation, I can only assume blood would be the next thing on the list.