In a recent email and subsequent store update, Blizzard has added a note that the Dark Portal Pass and Deluxe Edition from TBC Classic will be retiring from the store on August 29th. Some items from the Deluxe Edition may be available to purchase in the future.
The date fits perfectly with the Wrath of the Lich King Pre-Patch date, August 30th, meaning likely both will be replaced by their Wrath counterparts, but nothing has been confirmed.