Interesting thought processes. I have to say, Despothera, that your theories give me quite a bit to consider.

I think all of the signs, though, point to Perrin's death. Referencing the aforementioned prophecy, "The strongest thing I see about the big, curly-haired fellow are a wolf, and a broken crown, and trees flowering all around him." I think the trees flowering around him are the apple trees in the Two Rivers where the rest of his family are buried. Also, I think the dark prophecy mentioned in a previous post indicates that Perrin will perish, though the circumstances will likely lead to the victory of the Light rather than the inferred Shadow victory. Undoubtedly, he will live on in the world of dreams, but I do not think he will be involved with the rediscovery of the song.

I am torn between two theories for the rediscovery of the song. First, we can speculate that the Ogier with the Seanchan arrived in that land following the Breaking - as it is highly unlikely that would have traveled with Hawkwing's army. It is possible that those Ogier know the songs of growing. The other option is that the Wise Ones and Clan Chiefs already know the song from traveling through the ter'angreal at Rhuidean, but they only sing battle hymns and laments for the dead. If that's the case, either Rand or Aviendha could convince them to take up Singing.

I am unsure if the Tinkers, as contaminated as their blood-lines are, would even still have the Voice. It would be tragic if they were to find their elusive Song only to find they cannot sing it as it was meant to be sung.

I do not think that the Aiel (those following Rand) will all be destroyed in the last battle. After all, Aviendha's "viewing" showed her descendants' survival post Last Battle, so their sacrifice will not be required to defeat the Dark One. And of course, given Min's viewing, Aviendha will survive long enough to have her kids. I think that since those Aiel following Rand are "a remnant of a remnant", at least some (possibly many) will survive the Last Battle according to Aviendha's viewing, and given the importance of Egwene's agreement with the Wise Ones to cross-train women, the Aiel will most certainly survive the Last Battle in significant numbers.

That begs the question, how can the Aiel's skills be applied in a post Last Battle world in a manner that prevents Aviendha's 'vision'? From The Great Hunt:

"When the Trollocs come out of the Blight again, we will leave the Three-fold Land and take back our places of old."

I think they will again serve the Aes Sedai, though not in the same manner as before. I think they will remain warriors, most of them, but will form a strong alliance with the White Tower, working together to defend and rebuild Randland.

I like that you brought up the singing, as I think that is very significant: though not to the Last Battle. I can't help but wonder if, since Rand has all of Lews Therin's memories, he knows the songs and will teach them to the Tinkers and Ogier. Perhaps some of the Aiel will learn as well, as their blood is more pure than the Tinkers'.

Anyhow, that's my two cents.