Your question makes as much sense as saying IF President Obama beats his wife and kids would it be a non issue. Speculation does no one any good.
But to somewhat answer. any person running for pubic office who has broken tax laws, been convicted, or taken a plea deal, it would be good to know. I am not aware this is the case with Romney. Many people amend their tax forms to make corrections or additions to the submission without it being amnesty from the IRS.