I think you may be correct about JW getting traded but I think it may be after the season starts when another team is looking for a starting QB. He would be worth a little more at that point and it will give Heener more time to be in our system.
I think that's something both the team and Winston have considered as an option when they agreed to his new contract.
It doesn't seem like any team was willing to guarantee Winston a starting role and the Saints needed all the cap savings it could get. I think the Saints and Winston could have an agreement that if at any point another team is willing to give Winston a starting role, then the Saints will either cut Winston or trade him for a reasonable price to that team.