Based on this image from the "What the Teams are Working On" blog I think Saga is going to be Polish-Lithuanian-Teutonic focused. They've covered the period before, and they said that's what they're doing with the Saga title, a period they have done previously but felt didn't give it the attention it needed. They'd probably pick the Polish-Lithuanian-Teutonic War, as that would make for a good FOTS like campaign I feel.
Spoiler Alert, click show to read: