"Blizzard came out and said that not all the content would last in their official preview. I imagine it's because phasing a capital city for all level 90 players is a really bad long-term decision. It's best to think of this as a world event instead of a permanent content update."
Thank you for the answer. I've been trying to find the answer from the fansite interviews, it never occured to me to look at the Official Preview.
However, to me, it's a non-issue either way. Cosmetic changes, yeah, I can get why they aren't important to stick around, and until I get round to playing the Horde half of 5.3's content, I can't really dissect what is good and bad in either approach.
However, it's worth pointing out that there are multiple layers to phasing now. Blizzard do not need to purchase wow gold phase players anymore to get the same zone progression effect. For example, it is fully in the game's power now to have Abomination Guards in Undercity for players under level 73 and Kor'kron guards for players over level 73 and to allow players of all levels to still see eachother (i.e. Player A and Player B can see eachother, but player A sees Abomination Guards, Player B see Kor'kron guards). As long as there are no physical restrictions between the two versions (closed doors, holes in floors etc), there is almost no reason why and where to buy wow accounts Blizzard can't have multiple setups of a location now, and even less reason if the only differences are NPCs. As long as you have hard triggers based on character levels, soft triggers based on character progress in quest chains and NPCs available to port you into either version (like Theramore), there is no reason to remove any of this type of content.
I will abmit, I'm a bit of an obstinate bastard on this subject. I am not a fan of the history of this game removing imoportant moments in the story. I get story progression, I really do, but not sell wow accounts at the sacrifice of what came before. I am still nervous that they will eventually make the Ruins of Theramore the baseline version and the current sub-level 80 version will be gone forever, which will be very annoying. The story flow is a struggle as it is, we don't need players that choose to level in Dustwallow Marsh to go Cata > Mists > Cata > TBC > Wrath > Cata > Mists. It's unncessary as proven by the current setup of Theramore.