I am not sure that will have a big impact on margin of victory as all teams have the same potwntial to benefit from the scoring change in a given year, and MOV is a measure within a year that can mostly be compared across years.
Where it breaks down is when the difference between first and third, fourth, etc. changes from year to year. The winning team will place higher on average so bigger spreads lead to bigger MOV. Right now the spread is tighter than it has ever been making it harder to beat the Iowa record even with bonus point inflation.