You cannot even imagine that.
Look at that: "Defeating Archimonde on Heroic difficulty or higher will reward the Grove Warden mount (for a limited time)!" They want from you to come back NOW! So if you don't come back before the Legion you will not get that "almost shop" mount. Just look at the quarters they need to manipulate the numbers if they don't want to get some punishments from their management.
I like how they timed that 6.2.3 thing so people can calm down until Blizzcon.