Square Enix had recently released a brand new teaser site for 3 upcoming Million Arthur games.
Out of these 3 MA titles, MA 2.5 has already been out for quite some time now while MA 3 was recently released in China. MA 3 is slated to launch in Japan really soon while the last MA title, MA 4, will also be released in 2018.
More news will be announced in March when during the Million Arthur Press Conference.