If he were to do 5 for 150 after next season he could easily provide surplus value. I think the market is roughly 9 mil per WAR right now? I could see something like this as a realistic aging curve for him.
Age 33, 2019: 5.5 WAR
Age 34, 2020: 5.0
Age 35, 2021: 4.5
Age 36, 2022: 4.0
Age 37, 2023: 3.5