Too many people would be lining up for a replacement.. and it would just prove apple was wrong.
I would guess from a supply perspective they may be waiting for stores/retailers to be fully stocked with the revised model rather than announcing a recall and halting all sales. If there is a new model with antenna coating, it would almost make too much sense to allow all of the "old" models sell through at retail, the chain to be fully restocked with the new model, and then announce a recall. There would be no halt in sales, and phones would be plentiful for both recall swaps and new sales.
At east that's what I would do, and I've managed a messy project or 10.....