[whpalmer4]

Due dates have nothing to do with next actions. There is only one next action per project (*), and it is the uppermost action (when viewed in Project mode) which is available. That may not be the action with the closest due date...

(*) Single Action Lists show all of their available actions as next actions. You can have action groups in a Single Action List, so if you want to see a next action for each concurrent action group in your project, converting the project to SAL would accomodate that.