According to Tseric in this thread from the WoW.com forums, the WoW team is considering options to limit or outright eliminate a burst of XP from these methods. While I can understand they would rather have people enjoy the new content and not make a mad dash to 70, I can also see some folks who will be highly annoyed if they nerf this little XP scheme.
I know several guildies who have a questlog full of completed quests just waiting to turn them all in come the expansion. They also have garnered some other items they are going to use to pad their experience totals come the BC launch, like AD and AQ rep turn ins. I always thought that was a pretty clever idea, and they will have a headstart come BC at hitting level 61. I haven't done it, as I am not in any huge rush to level, but if getting to 70 ASAP is a goal, the stockpiling plan is a winner.
Any of you guys stockpiling XP? If so, how annoyed are you going to be if Blizzard limits or eliminates your XP?