After the Ixalan block this fall (see “'Magic: The Gathering' Adds 'Ixalan,' 'Iconic Masters,' 'Commander 2017'”) , there will be three large sets a year, with a revamped core set debuting in the summer months (beginning in 2018). Essentially, multi-release "blocks" with be discontinued. Each large Standard-legal expansion (Fall, Winter, Spring) will be drafted alone, and have its own mechanical identity (though there is potential for a small amount of overlap). The summer core sets will be aimed at new players, with some useful cards for enfranchised players (new and reprinted cards for Constructed play). The core set will integrate well with sample decks, Planeswalker Decks, and Deck Builder’s Toolkit. Overall, the core set will serve a different purpose (introducing new players) and will not be on the same “footing” as the other three sets.
(Click image to see release schedule through 2019.)
Beginning with Hour of Devastation (releasing July 14), Gatewatch characters will no longer be the main focus of the storyline. They will continue to play a role in the story, but not every member will show up in every block, or a future block may contain no Gatewatch character cards. They will continue to be used, especially for Constructed format play.
The Masterpiece Series will reduce releases after Hour of Devastation. The series will continue, but due to quality control concerns, it will not appear in every release. The Ixalan block will not include Masterpieces.
Wizards of the Coast switched to this new reveal schedule in 2016 (see “Major Plans for 'Magic: The Gathering'”), but delayed the March 31 announcement because they wanted to include more information on Magic’s 25th Anniversary. Then it became a week of announcements.
Tuesday’s announcement will cover upcoming digital offerings for M:TG and an updated banned and restricted list. Wednesday, WOTC will announce upcoming new products and worlds for the game. Thursday will cover a small Organized Play announcement that will debut in 2018. Friday will include the online streaming program Hour of Devastation on twitch TV, where WOTC will preview upcoming cards and cover action at the Grand Prix Las Vegas.