Board Thread:Manga/@comment-27321453-20180208183201/@comment-1327106-20180228211435

If you go to Bessatsu Shonen Magazine's web site you can see that they always release their issues one month ahead.

http://www.shonenmagazine.com/bmaga/index.html

You can click on the link, use Google translate, and then go down to the bottom of the page and you will see that their April issue is scheduled to be released March 9th.

http://attackontitan.wikia.com/d/p/3100000000000000641