So with 5.3 almost upon we can finally start seriously speculating some of the big changes we can expect in 5.4. The Siege of Orgrimmar, yay! Finally, we'll be (based on popular assumption) ousting Garrosh from power. The horde saw a lot of changes with Garrosh coming to power, both ideologically and physically. With Garrosh we got the new metal fortress orgrimmar and the suppression of the styles of the other races.
When Garrosh is overthrown, through both a combination of what I'd imagine as sheer destruction of Orgrimmar itself from the raid/story/war itself, and the .ore. orgrimmar is going to change again post 5.4.
The new orgrimmar is going to show a more unified approach to the horde and its races, showing a more equal combination of racial traits throughout the city. More defined quarters, possibly even a blood elf and undead quarter etc. This would make orgrimmar more along the scale of Stormwind in power. Stormwind is like NYC, a combination of all the races. Orgrimmar is more or less segmented into just a few of the total series of horde races. With the new orgrimmar we'll see ALL races contribute in style.