The big question is whether this future is set in stone or if it can be changed completely by decisions Aviendha will bring the Aiel to make.

The whole debate Aviendha is facing is what should the Aiel become after the LB.

The future she's foreseen is one that has not been altered from the time Aviendha left Rand, that is Rand still plans (and in this future succeeds) to enforce a truce between the Seanchan and the Westlands, and it solves nothing as soon after he's no longer around, the forces resume their war. In short, nothing got solved, the Seanchan merely postponed their war of conquest, their hatred for the WT and Asha'man is still very much alive, and the Aiel still intend to go to war against the Seanchan (a war of retribution, not too unlike the war they didn't call a war against Laman), and return to the Waste post TG.

There is no hint of the later (later than Aviendha's visit to Rhuidean) developments, like the fact the Seanchan have attacked the Tower, that Egwene has sowed the first seeds of an alliance of a sort between all female channelers, all the changes in Rand's character since his epiphany, nor even of Elayne's forming new "Empire". Rand as he is now is most, most unlikely to "enforce" any truce between the Seanchan and Tower or Westlands. LTT would understand perfectly well this would only lead to a devasting world war once he's no longer around. The new Rand would never try to impose a factice and dangerous peace like this on the world. Another thing that doesn't work with this future is that we know Jordan planned a sequel, set 5-10 years after TG, in which Tuon and Mat crossed the sea to go reconquer and pacify the Seanchan Empire - in other words, unlike Aviendha's future, it appears the Seachan leave the Westlands 5-10 years after TG.

The odds are Aviendha's foreseen future was part of the original purpose of the Glass Columns, as set up by the Aes Sedai of Rhuidean. This is not THE future, but a warning tailed for Aviendha, a future extrapolated from things as they stand now.

For millenia, the Aiel were shown their past so they did not forget what they once were (ask yourself why this is important...), and only their leaders knew this so their path and identity as the warriors they had to become to survive the Third Age was unhindered by pacifist factions trying to bring back the lost past, or to seek the Tinkers too soon etc. The Aiel leaders know this was their past, and that it could not be their present. They also know the "Lost Ones" still hold to the old beliefs, and could teach them again. I think the future shown to Aviendha is the final purpose of the Glass Columns, showing her where the future may lead if the Aiel remain warriors after TG and don't return to the Way of the Leaf and living among the rest of the people (and Aviendha's path is one where she's learned to abandon the Warrior ways and return to peaceful means... that and learn with Elayne the truth about her prejudices on other cultures..).

It's the finality of what the Rhuidean Aes Sedai had foreseen: the Aiel have an important purpose (which they still don't understand), and they could not fulfill it if they kept to the Way of the Leaf in the Third Age. The AS thought at first the Aiel had to keep to the Way no matter what, but they saw their mistake when the Jenn could not survive the Waste. For a long time, the Tinkers had to wander unable to find what they used to be or who they really were, and the Aiel had to adopt a rough warrior culture to survive. The AS set the ter'angreal up so the strongest and wisest of the Aiel would still be unable to forget when they came from. It's very obvious the Rhuidean Aes Sedai believed that when the Aiel would be needed, when the time of their purpose would come, they would need to return to the Way of the Leaf to fulfill it. The future Aviendha has seen is a warning, a trigger for a radical change to the Aiel culture that Aviendha, once she's thought it through, will bring about with Rand, perhaps at Rand's instigation (Aviendha's story might make him realize how he could use the Leafers and their "powers" in TG, in a way he had not done in the WOS). It all had to happen once Rand gained all of LTT's memories and the LB began. The Aiel would not have survived as Leafers before the Light was united as Rand didn't have the power to protect them, and Rand had to become in truth the Creator's champion. His passage through the Tinkers in Ebou Dar was no coincidence, just another tip from the Wheel...

Where does this leaves us? It sounds like the very dark future Aviendha saw most likely will be averted. Some events, like the birth of her quadruplets from Rand are set in stone, but most others seem to be extrapolated from facts "recorded" either by the Glass Columns, or by the Arches through which the WO see tons of variations on their future, some things that can only be accepted, and others that are just choices they'll face. The future seems one based on Aviendha's own soul thread and "possible futures", and possibly on Rand's.

The WO are trained to accept what can't be changed, and about the importance of making decisions as leaders. They gain a kind of second sense from the Arches, a feeling of déjà vu when they have to make important choices, in a way not unlike Mat's dices...

I think Aviendha triggered the "second vision" not by any Talent of hers, but because she's the woman the ter'angreal was programmed to show these visions to. It was always to be shown to the woman who would be the mother of the Children of the Dragon, IMO. The ter'angreal drew from her thread in the Pattern as she went though it, and then played back a kind of virtual reality version of the future as it could happen, if the Aiel don't return to the Way.

It's left to Aviendha and Rand to puzzle it out.

It seems very unlikely to me many of the events depicted in the vision will come true. All it revealed for certain, IMO, is how Aviendha's four babies are "odd" (and it's now clear why Jordan put that Viewing in... the vision is the final answer we'll get. Those babies will very doubtfully be born before the end of the series). The more remote the events shown are from Aviendha (and maybe Rand), the more extrapolated they must be. I doubt it tells us much about Elayne's real future, or Tuon's, or the WT's etc. I think it's a "futurustic" vision not dissimilar in nature to the Aes Sedai test for Acceptance. It's based on the person going in, and some elements are real, but few and far between.

The most interesting tidbit remains Nakomi, whose conversation was preparing Aviendha to ask herself the important questions about the future of the Aiel, the old ways etc. What would happen to the Aiel once it's all over is not something Aviendha had mused much on before Nakomi brought it up. It does sound a lot like Nakomi was more or less literally a Deus ex Machina, an intervention of some kind from the Wheel, a twisting of reality.