I did some research into this, here's eBay's official policy regarding pre-sale items.

eBay permits Pre-sale listings only on a limited basis. The seller must guarantee that the item will be available for shipping within 20 days from the date of purchase (i.e., the day the listing ends or the date the item is purchased from a store front listing). The seller must also clearly indicate within the listing the fact that the item is a pre-sale item with a delivery date that indicates the item will be shipped by the 20th day from the end date of the listing. Additionally, this text must be no less than the default font size of the eBay Sell-Your-Item form. Currently, the default font size is HTML font size 3.
Seeing as the items Griff mentioned don't really have a confirmed release date yet (and are too far into the future), that's most likely why there are none listed for pre-sale.