It’s more like proposing Xen’drik and Argonnessen because there is already a book on Breland, but none of the five nations...Nope. Sword Coast has a book, and there are options for Al-Qadim and Kara-Tur for people to choose.
If I allowed a general "the rest of FR" option I'd have to add one for Eberron (beyond Khorvaire) and Ravenloft (beyond Barovia), which I'm not planning on doing.
Planescape, Council of Wyrms, Dragonlance, Ghost walk in that order.
What is "Maharsapa", isn't "Iron Fist" by other now? Could WotC get the rights for a d20 Rokugan? If it is possible.... only humans could be members of the samurai clans?
Really I want the metaplot of Greyhawk, Dark Sun and Ravenloft continuing. But I am afraid this has to await because these are linked with the future media projects.
I would like a new Oriental Adventures, but with classes as samurai, ninja or sohei, and with interesting racial traits for the shen. I like shens' background but not their racial traits very much.
* I would dare to bet we will see a Spelljammer setting in this edition because is a line with magical vehicles, and Hasbro is wishing to sell D&D toys.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.