Not so long after we got information about the trademark registry for Khans of Tarkir, as a possible replacement set name for Warlords of Khanar, the Australian patent office has gotten a filing by Wizards of the Coast for a related name: Dragons of Tarkir. The filing has the usual language:
Class 9: Apparatus for recording, transmission or reproduction of sound or images; computer hardware; computer software; application software; interactive entertainment software, including computer game software, computer game programs, computer game cartridges, computer game discs; downloadable software for use in connection with computers, portable gaming devices, console gaming devices, communication devices and mobile telephones; printed publications in electronically readable form
Class 28: Toys, games and playthings
Class 41: Education; providing of training; entertainment; sporting and cultural activities; publication of books, magazines and journals; publication of electronic books and journals online; publication of multimedia material online; providing online electronic publications (not downloadable); organisation of competitions
There's no question that the registrations are actually legitimate, but whether they'll actually get used is up in the air. Still, the fact that there are two apparent set names with the Tarkir plane name in them as opposed to Khanar means the most likely scenario is that Khans of Tarkir will start off a block, and Dragons of Tarkir may well be the second set. This would be the first block with the plane name appearing in more than one of the sets - that is, beyond the first set - since Scars of Mirrodin was followed by Mirrodin Besieged, but it's not otherwise unheard of; witness Alara Reborn at the end of Shards of Alara block. The fact that there's an "of Tarkir" formula means that we may be seeing all three (or more) sets having this name structure, a la Kamigawa block.