I think it would be awesome to have new campaign books written by and for different nationalities and then translated back to English. Imagine a MM written for southeast Asia, incorporating some of the weird monsters D&D has always had but including cosmology and monsters from their heritage? What would we have instead of demons and devils? What kind of awesome takes on ghosts and vampires could they have?We shouldn't forget the potential of the international market. D&D is known thanks the videogames, but it is not as famous as other Hasbro's franchises, for example Transformers. Critical Role has helped very much, but that in the English-speaker market. (OMG! I don't want to imagine a game-live show with Latin Spanish-Speakers!!).
Of course WotC may make mistakes, but everybody share that risk.
Could D&D become "old-fashioned"? It is possible if there is a saturation, but WotC can avoid this with new settings enough original.
Hard to say if it would sell though, there is a possibility of backlash no matter how carefully done.