My theory is that some Aiel will re-swear the Covenant of the Da’shain and adopt the Way of the Leaf before the Last Battle, and thus go back to what the Aiel originally were in the Age of Legends. Maybe in a mirror of the Breaking, the Aiel warriors protect the Aiel who re-adopt the Way (the new Jenn!) just as we saw in The Shadow Rising.
Just about all of the Aiel prophecies talk about the Aiel either being broken by the Way or by Rand, and of them re-gaining their former greatness, their old places, and what was theirs and was lost:
"When the Trollocs come out of the Blight again, we will leave the Three-fold Land and take back our places of old…”Their places of old were serving the Aes Sedai and the Dragon in the Age of Legends with their purity borne of following the Way of the Leaf. They failed the Aes Sedai when they abandoned the Way and this led to them losing their Singing ability. In The Gathering Storm, Egwene searched with need for something necessary to preserve the world in the Last Battle and found herself in a Tinker’s camp, again indicating the importance of the Way. (However, I think the Tinkers do not fully follow the Way as the Da’shain did. More on this below.)
- The Great Hunt, A New Thread In The Pattern
"we will be changed, and find again what was ours, and was lost."The Aiel were changed by the discovery of their true history and by the bleakness, and their customs have been changed also by Rand, by Sevanna, by being out of the Waste and by events. The Aiel might not yet have changed enough though. "What was ours, and was lost" is the reverence and honour the Da’shain Aiel had in the Age of Legends, earned by the purity and sanctity of the Way of the Leaf. The Way gave them special abilities including that of Singing. The World of Robert Jordan’s The Wheel of Time says the Da’shain could "often enhance channelling" with their singing, which is an interesting hint of why their Singing is important for the Last Battle and that it was more than making crops grow.
- The Dragon Reborn, A Different Dance
"he will come from Rhuidean at dawn, and tie you together with bonds you cannot break. He will take you back and he will destroy you."I think the bonds the Aiel cannot break will be those of the Covenant – to follow the Way of the Leaf and to serve. In a smaller way, clans that had blood feud have now sworn water oath, which is a pretty unbreakable bond. Rand has taken the Aiel back to the wetlands, and may also take them back to not just serving the Dragon, but serving him in the way they used to as Da’shain Aiel, following the Way of the Leaf. He is destroying them – the Shaido and Brotherless are renegades, many Aiel are being taken by the bleakness and running, and many of them have died or will die in battle.
- The Shadow Rising, The Road to the Spear
"He shall spill out the blood of those who call themselves Aiel as water on sand, and he shall break them as dried twigs, yet the remnant of a remnant shall he save, and they shall live."The Aiel will be killed in great numbers – though so probably will all peoples. If they do re-adopt Da’shain vows and swear to do no violence, they will be very vulnerable and they won’t be able to save themselves. Hence Rand doing so. The Aiel themselves are a remnant – of the Da’shain.
- The Shadow Rising, He Who Comes With The Dawn
I don't think they have been broken much at all yet. Other nations have done far worse and yet are not prophesied to be destroyed as the Aiel are. Nor have the Aiel regained what they had. The Aiel are a remnant – of the Da’shain.
Those who re-adopt the Way of the Leaf and are dedicated to do no violence will be very vulnerable and won’t be able to able to defend themselves. Hence Rand saving them.
The simplest way for this to occur would be for some of the Aiel to be convinced they need to adopt the Way soon and serve as the Da'shain did. This would really break the Aiel, going against everything they've done in the last 3000 years. Rand would have to save them, protect them as the Aes Sedai protected the Da'shain during the War of Power.
What Aviendha sees in Rhuidean (both within the glass columns and in the city) may be the trigger. There she was going on in Arad Doman about regaining her honour by becoming a Wise One, and she's about to learn that the Aiel have no honour as far as Aes Sedai (and Rand as the reincarnated Dragon) are concerned. Oh dear. No wonder the Aiel prophecies say the Aiel will be broken.
I believe that Singing and the Da’shain’s ability to ‘enhance channelling’ with their singing is required for the final confrontation of the Last Battle. The Aiel would have to adopt the Way soon, since the purity of the Way presumably takes time to have an effect.
I like the irony that the Aiel regain what they never searched for and the Tinkers searched for something they can't gain (without the Aiel).
The Tinkers' Way of the Leaf is a remnant version of what the Da'shain Aiel’s Covenants actually were; otherwise the Tinkers would not have lost the Singing ability. True, they lost all circumstances where they might have used it during the Breaking, but they seemed to lose the skill rapidly as well.
And Lews Therin asked Ishy:
"Have you the Voice, stranger? It will soon be time for the Singing, and here all are welcome to take part.”which suggests it had a religious or meditative role.
- The Eye Of The World, Prologue
The Way of the Leaf is as much about sharing, warmth and compassion as about peace and non-violence. Even during the Breaking they gave freely to others.
To share was the way. To give freely.They gave of themselves freely too to the Aes Sedai and the community. (Rand must do this also at Shayol Ghul.)
- The Great Hunt, The Dedicated
The Way gave the Da’shain special abilities including that of Singing. The Aiel may need to regain these before Rand’s confrontation with the Dark One.
If we look at the closest real world equivalent of the Da’shain, the Jain, they take five major vows: to protect all life and abstain from violence (defined as not injuring, abusing, oppressing, enslaving, insulting, tormenting, torturing, or killing any creature or living being), to speak the truth (unless it would cause a greater violence), not to steal, to be chaste, and to limit possessions. They aspire to kindness, compassion and reverence for all forms of life in speech, thought, and action. Other vows
involve avoidance of unnecessary travel, of harmful activities, and of the pursuit of pleasure; fasting and control of diet; offering gifts and service to monks, the poor, and fellow believers; and voluntary death if the observance of the major vows proves impossible.Their code of non-violence means caring for and sharing with all living beings and tending, protecting and serving them. It entails universal friendliness, universal forgiveness and universal fearlessness. This seems very close to what the Da’shain represented.
- Encyclopaedia Britannica
When one considers what the Jain are like (and thus the Da'shain) and what the Aiel are like, one can only wince. For instance the Jain wear veils to prevent themselves from breathing in insects and thus injuring or killing them, while the Aiel veil themselves before they kill.
Those Aiel affected by the Bleakness who believe they should stay gai’shain have something like the right idea, but they're not serving. Neither are the Tinkers. Formal sworn service and following the Way to do absolutely no violence and to share freely of themselves seems to be what is required.
The Aiel can't take them back their places of old until they follow the Covenants and they can't do that until they re-adopt the Way. The Way comes first - and before the Last Battle. Each Aiel will have to decide which is the more important thing to follow: the Way or the call to military battle. While the Aiel warriors are great fighters, channellers fight Shadowspawn better still and so will Mat's cannon.
Long ago, in the Age of Legends, the Tinkers’ and Aiel’s ancestors, the Da’shain, and the Ogier Sang together. Singing itself, and its channelling enhancing properties, and the vows of service to all will be needed again at the very end of this Age, or is it the beginning of the next? Quite possibly without the new Da’shain Singing Rand cannot beat the Dark One or the Fourth Age dawn.
It’s interesting that representatives of all three groups – Ogier, Tinker and Aiel - were with Perrin and contributed to the great victory in the Two Rivers. From the beginning of the series the Two Rivers has been a microcosm of the whole World, so I think that representatives of the Tinkers and Aiel will re-adopt the true Way of the Leaf and make a covenant with the Dragon during the Last Battle, enabling them to Sing with the Ogier as in the Age of Legends.