It depends - if you opt out for any strongly-held reasons then you would presumably not wish to receive a donated organ for those exact same reasons. I can't think of any single legit reason to penalise people who opt back in by making them wait a year before they qualify to receive though, that just seems petty and vindictive. In principle opt-out sounds okay, in reality I object to the idea that our government gets the default right to cut me up like a car at the breaker's yard, no matter how many lives it may save in theory.