Actually, I think Apple could ride out a 6 month product delay quite easily. It would seem that the 4S was delayed 3 or 4 months (part shortage resulting from the earthquake in Japan?) from the normal summer release with no ill effects. Releasing it in December would have been bad, sure, but that has more to do with Christmas than the length of the delay.
I'm thinking more the kind of delay where the product is already on the market and a part shortage stops production, leaving Apple with nothing to sell.
