Do you think Manabe plans to take back Ishii and Nagaoka to the NT? Does anyone know when they will retire?
Not sure, they could retire at the end of the 2022-2023 season.
I don't think he'll take them back, unless there's a very very good reason too. An example would be like the China Women NT, where they had Yan Ni (MB) in the NT up until the 2020 Olympic Games even though she was 33/34 years old then. They did that because she was a superb MB, quite unparalleled by any other Chinese player due to her skill at reading the opponent and positioning her block. She didn't have the highest vertial nor the strongest spike like her younger teammates, but she was a stable force to be reckoned, a Great Wall of China.
Unless Ishii and Nagaoka have that kind of potency which would benefit the Japan NT, even at the opportunity cost of obtaining and training younger talents, then I don't think these two will find themselves in the NT again anytime soon