Elves after Arda is Remade

[Lachwen]

Actually...this is dealt with in The Lost Road and Other Writings, at the end of the section describing (though not in great detail) the Last Battle:

…Thereafter shall Earth be broken and re-made, and Silmarils shall be recovered out of Air and Earth and Sea; for Eärendil shall descend and surrender that flame which he hath had in keeping. Then Fëanor shall take the Three Jewels and bear them to Yavanna Palúrien; and she will break them and with their fire rekindle the Two Trees, and a great light shall come forth. And the Mountains of Valinor shall be leveled, so that the Light shall go out over all the world. In that light the Gods will grow young again, and the Elves awake and all their dead arise, and the purpose of Ilúvatar be fulfilled concerning them.

So it sounds to me like all the Elves there ever were have, basically, a huge honkin’ party. Now, I don’t know what is meant by “the purpose of Ilúvatar be fulfilled concerning them.” What do you guys think it means?