Looks like Blizzard is going to retire the Deluxe Edition for Mists of Pandaria. So if you still miss the Imperial Quilen mount or the Lucky Quilen Cub pet and you really want them this is the time to purchase the Deluxe Edition. Blizzard said that the Deluxe version might be available again in the future, but we don’t know when.
If you already have the MoP Standard version you can upgrade it.
The deluxe edition of MoP also contains an unique Diablo 3 Banner Sigil and Accent and two unique Starcraft 2 portraits.
If you want to buy it or to upgrade your standard version move fast, this Deluxe Edition will be gone after March 10.