That's right.
All iPhones Apple will have in store will be unlocked to begin with - maybe that's what they mean. It's when the contract is attached to the SIM card that the phone becomes locked.
Otherwise Apple would need to order in specific numbers of network locked units beforehand, which is just inefficient as they have no idea what demand will be like on the day. Much easier to have 2 stock models (16gb/32gb), unlocked, whose price and lock status is determined at the point of sale.
There is a chance that all phones sold will be unlocked, of course. I just think it's incredibly unlikely. The networks are subsidising the cost of the phone by as much as £250-599 depending on contract. Generally they want it locked down.