There’s no way to look up past incentives, aside from someone working at a dealership who might have access to those records. I have been recording the RWD incentives manually in a spreadsheet, month by month.
In a way the salesman is right - no way of knowing exactly what incentives will be in a year. Chances are, they won’t get any worse. However, it’s possible that Kia could increase their residuals and lower the MF, while reducing lease cash and arrive at the same payment. Not likely, but possible.