Magic, for all intents and purposes, started on Dominaria. Sure, Alpha, Beta, and Unlimited had no plot to speak of, but they used setting and character names that were later to be associated with the plane of Dominaria; and although Arabian Nights, the first expansion, was retroactively deemed to be set on the thousand-faceted plane of Rabiah, both the early standalone expansions (Antiquities, Legends, The Dark, and Fallen Empires) and the first few blocks of Magic were set on Dominaria. That world is and was huge and diverse, having been the setting for seven full blocks and other scattered sets besides, but its story seemed to have ended with Time Spiral block, which aimed to bring a fitting conclusion to the fractured and fraught history of the most fought-over plane in the Multiverse.
But perhaps the Time Spiral Crisis wasn't the end: Mark Rosewater says not.
When bioboy66 asked, "Will we ever see a 'return to Dominaria' expansion?" Rosewater responded:
I assume one day.
I've already covered the massive turnout in favor of such a "return to Dominaria" set or block that resulted from a straw poll Mark Rosewater took last year. Community ideas for that block are detailed in that article, but in the comments of this question on Tumblr, commuterist voiced the thoughts of probably many readers, saying "I’d take this as meaning that the idea has at the very least been creatively concepted." After all, the actual process of rebuilding after the "residue of apocalypses" put an entire plane in a state of decay needs explanation, and Rosewater wouldn't make such promises if he didn't already know a good reason.