My nearest Woolies has also started stocking bags that don't have the competition on it, so after this week of specials, it might be hard to find competition bags at the two major grocery stores.
Even though the T&Cs allow for any Doritos bag of the noted sizes and flavours (because they have the same barcode), they do also note that the Promoter's decision is final... so could be picky and reject anyone who didn't buy their product with the Transformers competition on it. (I didn't want to risk it, so bought up some competition packs this week... and will spend the next few months slowly eating through them... very slowly, because I'm not much of a fan of Doritos)