In my experience of Amazon, and I've been a Prime member for a long time, they honour all orders even if an initial delay due to no stock. They've never cancelled on any order I've made with them unless I wanted it cancelled.
Personally, I would a actually call up directly and talk to a CS representative to find out the current situation and try and get a firm date when you can expect to receive your order. They're red hot on keeping customers happy, Prime or not.
Apple would not definitely not honour those mis-prices for anyone but, likewise, they wouldn't mis-price like Amazon did on pre-order day.
Also, only a small handful of other businesses would actually do what Amazon have done to not only honour the mis-prices for everyone but not either demand full payment or cancel orders from customers. We are not talking a few quid, these are £1K phones. It's great it's actually happened for the Amazon pre-order crew.
They would rather keep those customers happy, take an initial small financial hit on pre-orders but gain existing customer & media kudos, especially with Black Friday coming.
Amazon will sort you out, I'm sure of it.