There were two UA articles about modern setting. If WotC wants modern/sci-fi settin within D&D OK for me, but it is a challenge about balance of power with different playable factions and theses with different level of magic and tech. Firearms are as the cheaper version of expensive magic item you are saving until the final fight agaisnt the supreme dungeon boss monster.
I dare to say Ravenloft will be before Dark Sun. And the first books will neither the player handbook nor the tourist guide of the region but the modules of the grand conjuction and maybe also the module of the house of the gryphon hill.
* I wonder about DM Guild allowing to seel DS tiles neither fluff nor crunch, but only sketchs and concept art, not only for DS but also Mystara Hollow Earth and Jakandor.