Managing stock levels is the bane of a small business. Well, one of them at least.
We set a product to pre-order status as soon as we're confident of the date we can actually ship the product. If you add a pre-order item to your cart with other in-stock items, your entire order will be placed on-hold until all items are in stock. This helps us keep our shipping costs, and therefore product costs, down. However, if you'd rather we ship the in-stock items immediately, please either let us know in the order notes, or simply place two orders, with the pre-order items in their own order.