Egwene's and Rand's story lines are supposed to be short-ish in ToM, and pick up fairly late in the book (timeline wise, anyway).

IMO, things will indeed build up to an attack by the Seanchan on the BT/Caemlyn.

But I think it will also build up with Logain sitting "forgotten" and useless in Illian for over a month while Rand "negotiate" with the Seanchan. But Logain is getting quite pissed and thinks the Asha'man have much more important things to do they wait doing nothing - deal with Taim notably. In the end, he will decide to disobey Rand and go straight to Egwene, perhaps after learning there are many sisters at the BT. It will come out that he's the one who bonded sisters, not Rand. But it will also come out that Rand has dismissed Logain's warnings about Taim and told Egwene to send envoys to the BT without forewarning her that Logain thought Taim a DF. Logain will learn that while Rand "negotiated" with the Seanchan, they have attacked the White Tower. Egwene will be furious at Rand, for Taim and for trying to negotiate with the Seanchan.

On the Tower side it will have built up with bad things having happened to the "rebel" embassy, and eventually the fact the Red envoys have vanished will come confirm something is very wrong, but before/unless Logain explains it, Egwene will conclude Rand, who sent an envoy to set this in motion, is behind this. By dismissing Logain's advice, Rand has not provided Egwene with 47 Asha'man, he's lost her an unknown number of sisters, perhaps close to 50.

It will also build up to the discovery, or guess, that the Black Ajah has joined Taim. This may come from Elayne, maybe.

Egwene and Logain will make an alliance without Rand, and strike together at the BT. Mixed gender circles, san'angreal - all they have.

Personally, I tend to think Rand won't be coming to Caemlyn with an army, but (not so very long after the end of TGS, timeline wise) secretely with Min and Aviendha, with the intent to marry all three, and the Shadow will strike (perhaps forewarned by Mesaana near Egwene that a big strike is coming). Egwene and Logain's army will arrive to fight Taim but late, the Seanchan might come to fight everyone, also late. I think Perrin will come with the Bordermen, while Mat is at Ghenjei or on his way back and will arrive to take control save what's left of the Light's forces. The battle that launches TG, will be very costly but bring about the uneasy alliance of all the forces of the Light.