From what I've read, it seems incredibly unlikely these will be honoured. Your contract isn't until they send the dispatch email, at which point they actually charge your card.
The only thing that makes me a tiny bit hopeful is that Amazon are pretty new to selling Apple products, and cancelling pre-orders for the biggest tech product launch of the year is hardly a good look, especially when some people will be selling on their phones and potentially have to wait weeks until they come back into stock. They might decide to suck up the cost.