Originally Posted by Valnoth (Source)
Below is the basic progression map. Obviously your mileage may vary, i.e. If you're Paragon or Premonition you will be able to skip some of the below and/or mix and match at your discretion.
*Normal Dungeons/Crafting/Questing to get full set of 85 blues (non-heroic) to do Heroic dungeons.
*Heroic dungeons to get full set of 85 Heroic blues to do Normal mode raids.
*Normal raids to get full set of 85 epics (non-heroic) to do Heroic mode raids.
*Heroic Raids to get full set of 85 Heroic epics, which will presumably help a bit on Sinestra and the next tier (when released with patch 4.1.0)
*Badge vendors to help fill in gaps at all tier levels.
*No real gating to speak of for ship.
*Sinestra opens after Cho'gall is defeated on HEROIC mode. No timers or attempt limits, but she will pound you relentlessly. She has better than Heroic epic level gear (half a tier better).
What makes this very believable is the fact that he is one of the lead world designers. So we may want to keep this info in mind while we gear up in Cataclysm. I will probably create a sticky post later where I'll start summing up all this information as I find it to save look up time in the forums.