In case you hadn't heard already the first set of raids in MoP will have a staggered release schedule, this schedule is as follows:
September 25: MoP launches
October 2: Mogu'shan Vaults (normal) opens
October 7: Mogu'shan Vaults (LFR) opens, those who cleared normal Vaults can access heroic mode
October 30: Heart of Fear and Terrace of Endless Spring (normal) open, with Terrace only accessible by clearing Heart
November 6: Heart of Fear and Terrace of Endless Spring (LFR) open; queuing for Terrace requires clearing Heart. Those who cleared normal Heart can access heroic Heart, same for Terrace.
Can't say I am a fan of being locked out of raids for a week after launch..or LFR being released only a week after content comes out but I am a fan of staggering releases anyways hope this is helpful!