I really enjoyed the Oriental Adventures setting for 3rd edition and I really hope someone, whether it's WoTc or a 3rd party (Here's looking at you Sasquatch), puts out an oriental setting. I would love to see classes and monsters done with the 5th edition rules.
Probably not as such... As in, don't expect it to be called "Oriental Adventures". The use of the term "oriental" was not well received when the 3e OA was released, so it's unlikely that they'll use that title again. I'd expect what you're looking for will be part of a Kara-Tur setting book if anything.
I also doubt that we'll many of the classes that were in either the 1e or 3e OA, especially samurai, bushi, ninja, or yakuza—as there are too many variations on those that they don't fit neatly under a single umbrella (and existing class/background combinations already do a great job of covering many of the variations). The wu jen really doesn't need to be a class, either—at best, it'd be a subclass of wizard (but given that its only claim to fame was an initiative bonus, and its use of the Chinese "elements" rather than the Greek/Indian/Buddhist elements, it's unlikely, IMO). Sohei might be salvageable as a paladin subclass, and the shukenja (1e)/shaman (3e) might make for a druid or cleric subclass or some sort of shaman base class. Kensei might make for a decent fighter or monk subclass. And the 3e shugenja is very Rokugan-specific and unlikely (at best) to be addressed. I'd also expect the classes to be renamed something generic (like kensei becoming "weapon master", shugenja becoming "shaman", etc.).
As for races, there's a lot more to salvage there (just don't expect the Rokugani Nezumi). Hengeyoukai, Korobokuru (more properly, Koro-pok-kuru), Spirit Folk, and 3e's Vanara all (mostly) add something to the game.
There's also some equipment that could be added (though most of the weapons—outside the weirder ones—and armor are already covered in the PHB). As an aside, I find the inclusion of the "o-yoroi" Japanese armor in the OA books kinda funny (given that it was an older, pre-Sengoku era armor and is pretty much the equivalent of scale armor).
If WotC chooses to revisit Kara-tur, i'd like to see an effort made to make it less japano-centric. At the very least, i'd like to see elements inspired by "Journey to the West" be as prominent as the "Lord of the Rings" inspired bits are in the D&D basic game.
Absolutely! It's funny that of the classes that were introduced in 1e's OA, other than the Wu Jen (the Monk and Barbarian had appeared earlier), all had Japanese names are were Japanese-inspired. And while the Wu Jen was inspired by the Chinese Daoist mystic, it's name was entirely made up (taking the Chinese characters for "magic" and "person"). I suppose it's more generic than "daoshi" (not that that got in the way of the shugenja), but given the otherwise Japanocentricy of the book, they could have gone with "onmyouji".
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