Eleannor
Azeroth's Champion
Good god, I missed that. Would you point me to the right place again to find that in the interview? While I admit I'm going speculation crazy this week, saying that they might "add" Cataclysm is HUGE [...]
It is as @Chops said. In an interview (too lazy to find it), they said all expansions will be available to level from 10 to 60. That might mean the 80-85 content added in Cataclysm (Ex.: Uldum zone, Stonecore Dungeon etc.) will be available.
In fact, I believe Cataclysm Chromie Time requires level30 is because Blizzard wants you to get a Flying Mount before questing there (which should not be a thing, since they have added pseudo-flying mounts for questing before).
You can get some of my reasoning in this Forum Post (which you guys can repply for more exposition).