The Nokia Shop says if the price is lower between the time you pre-order and when it is shipped, they will charge you the lower price.

On the other hand, the terms and conditions also allow them to change their mind about an order placed through the site, in case they accidentally gave the wrong price. They seem to have applied that when correcting some pre-orders that were made with multiple discount codes (in fact making it a better deal for the customer), and dishonoured cashback referral agreements in the process (not so good).