Is this just speculation, or do we have concrete reason to believe this? I understood the original intent was to split AMoL into three books of roughly equal length.

In any case, although your points are well made, I can't see the Egwene-Tuon alliance and their subsequent confrontation with Rand happening at the peak of TG, at which point Rand would presumably be in the front line rather than negotiating behind the scenes. Still, we shall see.

EDIT: There is also the issue of communication to take into account. If TG were at its height when the alliance is made, how could Tuon, and the forces of Rand/Egwene come to that, get word of their truce across in a timely manner to their forces fighting across the world, even with the aid of traveling? Everything would presumably be in total chaos at that point.