In Monday’s edition of the Magic Arcana at the mothership, Wizards made an announcement of the third set of the Theros Block: Journey Into Nyx. The set will be released on May 2nd, 2014 with prerelease events on April 26-27, 2014.
More details of the Journey Into Nyx set on the link below.
http://www.wizards.com/Magic/Magazine/Article.aspx?x=mtg/daily/arcana/1361