I think the Wessex and Mercia plot line indicates there will be some Viking involvement there pretty soon…most likely Ragnar learns of his son there and sails off to see him, on the way back to Paris. Likely takes the new Monk with him as an interpreter.

How do you tell the story of the Vikings and not tell the story of their activities in Britain and France? There's a region of France called "Normandy" after all.