[Edi]

I haven't read any of the stuff that came out since 3E was introduced, but even with 2E there was plenty of stuff about Tabot, Khazari, Wa, Kozakura, Shou Lung, Tu Lung and the Hordelands. I also have most of the stuff related to Zakhara, so that would not be a problem.

In the old material the areas that have the least coverage are the places south of the Sea of Fallen Stars between Chessenta and Tethyr (Chondath, Sespech, turmish, Orsraun, Shining Plains) and the Shaar and Eastern Shaar areas. Not much about the Black Jungles and the Mhair either.

Everything else has something even in the old stuff, though the greater part of that concentrates on the Dalelands and the Sword Coast North. Kara-Tur has less, as there were relatively few adventure modules made for it and just the one boxed set and what precursor stuff was in the 1E Oriental Adventures book.

There would still be enough to do nations and such based on those if you wanted and plenty of special provinces for a map, but specials would have to be redone anyway.