No. By doing the 2013 2-unit exam, you will get an aggregate that will be used to determine your aggregate in 2014.
This aggregate for 2-unit 2013 will be the same value as put into your 2014 aggregate.
However, depending on the year group, different aggregate's have different ATARs, as your ATAR measures your rank out of everyone else in the state. Just because your aggregate this year for 2-unit was worthy of being in the top 2.9% of the state, doesn't mean that next year it will be worth the same. It could be worth for the top 2% of the state (Cohort of 2014 does worse in the HSC than 2013 cohort) or top 5% of the state (Cohort of 2014 does better in the HSC than the 2013 cohort).
Generally, this is a gamble that accelerated students have to take.