Orgrimmar will definitely feel weird when this is all over, but on the other hand - I never saw a huge influx of Mag'har Orcs on Azeroth so far. Hellscream's Honor Guard in Northrend as well as Kilrath. Hellscream's Elite Guard during Silverpine's meeting with Sylvanas. Kromush, General ?Greebo? and Saurboz the Incinerator. It goes without saying that we still got some option for new NPCs, and perhaps some Dragonmaw/Blackrocks who survived - I'm sure some loyalists to Garrosh will also survive the Siege. Can't kill them all.
EDIT: Never mind, some Mag'har are in Siege. Whelp...Orcs are fucked.