Blizzard learning from their mistakes? Drysc says they most certainly did and are taking measures to ensure that the opening of the Dark Portal is not a lagfest like the Ahn'Qiraj event was.
For those that can't access the WoW forums, Drysc hints that the Dark Portal event will not require being anywhere near the portal to enjoy, and the event won't encourage people to gather there. In a nutshell, they are trying their best to avoid the player clumping that everyone experienced at Ahn'Qiraj. I remember the AQ opening on Bloodhoof, and it was a mess. I imagine most servers were the same.
Good news if this works out. The Dark Portal opening will be a massive event, and everyone deserves a chance to experience it.