Says the company:
During a limited time window, you will be able to place an order for the OnePlus One. If we have the items in stock, we'll ship immediately. If we don't, it will automatically become a pre-order. No matter what, we'll always tell you our best approximation for when it will ship before you submit the payment authorization (we'll reserve the payment and charge you when we ship).
There's a time limit, but no limit on the amount of orders that can be made. If we get a lot of pre-orders, we'll simply show you a longer shipping estimation date. Any time after the pre-order time window closes, you'll be able to forfeit your place in line, cancel the order, and release the payment reserve if you don't wish to wait any longer. If you receive an invite while waiting for a pre-order to ship, you can apply it to skip the pre-order queue and have your order shipped immediately.
To avoid panic, you'll be able to set things like address and accessories up well in advance (we're talking days here!), so at that final moment, all you have to do is press a button. We're looking to launch this in late October, and we'll have final instructions up a week before the pre-orders start.
Source:
OnePlus.Net