I said in another comment, but the idea that the known world in Azeroth is but one hemisphere of the whole, doesn't add up to me, even with retconning.

I've pointed out Durotar/the Barrens as being fech fech wastes/tropical savannah respectively being consistent with the equatorial latitudes they occupy.

I've also pointed to the heavy maritime activity present across Azeroth, but Stranglethorn Vale in particular, including an autonomous pirate rump state, who would have assuredly been trading with any Eastern Kingdoms or Kalimdor sized continent due south.

Lastly, I cannot recall where, but I know that at some point in the past, I saw an FMV which showed Azeroth from Orbit, demonstrably showing the two super continents to cover the globe sufficiently to leave little room for additional landmasses, short of new ones sprouting from the waves, which Blizzard have used as a magical MacGuffin enough times previously. Retconning would resolve this last one, but I thought it would bear mentioning. I just wish I knew from where I saw the clip. It was definitely made by Blizz.