From what I hear, the last three books are based on what RJ had planeed for the final book. TGS and ToM are based on the first two-thirds of what he had planned. Sanderson broke up the plotlines for Rand and Egwene for TGS and ToM is supposed to be more focused on Mat, Perrin, and various minor characters. As suggested by the cover, Mat's long-awaited journey into the Tower of Ghenjei should be one of the biggest parts of the plot. The final book, Memory of Light will be the climax of the whole series, and is supposed to cover the events of Tarmon Gaidon.