Moridin and Demandred are working together on some strategy. Therefore Demandred told Moridin in TGS: "My rule is secure. I gather for war. We will be ready."

That implies that Demandred, as a former general, has armies and rules a country. We also know that Moridin is gathering the Shadowspawn armies in the Blight and will apparently command them to go south, possibly together with SH.

In my opinion, the simple plan is that Moridin/SH will attack the Borderlands from the Blight. At the same time, Demandred will probably attack Andor with Roedran's army from Murandy to prevent that Andor supports the Borderlands, "marches to TG", as Elayne put it in KoD, ch.35. Probably Taim & his cronies will support Moridin's and Demandred's troops. Likely Demandred and other Forsaken will then also order Dragonsworn Bands and DF under their command to strike everywhere they can. If Demandred also controls the new rulers of Tarabon, they could also attack the Seanchan forces. In any case, the result will be major chaos in basically all of the Westlands, especially if the DO's power to spoil and twist reality will yet increase and become more target-oriented.

If this attack will already happen in ToM or in AMoL, remains to be seen, but I tend to think it will already start in the end of ToM (the blurb also says that the Last Battle starts in ToM). Then Demandred's identity will likely be revealed as well (perhaps either a prominent person on Roedran's court or Roedran himself).