Yeah the srancs-on-a-plain scenario has largely been played out. We are going to get something new, and the first big fight will be for Dagliash. I agree with you MG that once they are in, probably before they secure the fortress, the sranc with start pouring in.
If the Ordeal makes it past Dagliash, they will have a horrifying dash across Agongorea, similar to the trail of skulls in WP, and a largely defeated Ordeal will run into Golgotterath, where untold atrocities will pour from the dread gates....