So, do you think JAL will have 10 seats across on A350-1000 in Y? Also, will that make 8 seats across in PY of A350-1000?

Airbus website still lists the maximum cabin width as 18 ft. 5 in. Do you know if the current production A350 has switched to 18 ft. 9 in? Also, the contract for A350-1000 between JAL and Airbus was finalized before 18 ft. 9 in the cabin was introduced, I do think it will require contract modification (which will obviously affect wire and other settings on the aircraft, including the final cost of the aircraft) if JAL wants 18 ft. 9 in cabin width on their A350-1000. Also, to have maintenance commonality with their A350-900, it is possible that JAL wants 18 ft. 5 in cabin for A350-1000.

Airbus debuts new A350 cabin that seats 10 people a row to compete with Boeing's new flagship 777X - look inside